An Etymological Dictionary of Astronomy and Astrophysics

The Sculptor’s Chisel. A small inconspicuous → constellation in the southern sky, representing a sculptor’s chisel. Its brightest star, Alpha Caeli,
is magnitude 4.5. Approximate position: R.A. 4.5 h, Dec.: -40°; abbreviation: Cae, genitive form Caeli.

Etymology (EN): L. caelum sculptor’s “chisel.”

Etymology (PE): Qalam “chisel,” from Ar., related to L. caelum?

The Sculptor’s Chisel. A small inconspicuous → constellation in the southern sky, representing a sculptor’s chisel. Its brightest star, Alpha Caeli,
is magnitude 4.5. Approximate position: R.A. 4.5 h, Dec.: -40°; abbreviation: Cae, genitive form Caeli.

Etymology (EN): L. caelum sculptor’s “chisel.”

Etymology (PE): Qalam “chisel,” from Ar., related to L. caelum?

1. An enclosure, usually made with bars or wire, for keeping birds or wild animals.
   

2. An enclosed structure resembling a cage. → observer’s cage, → Faraday cage.

Etymology (EN): M.E. from O.Fr. cage, from L. cavea “hollow place, enclosure for animals,” cognate with Pers. kâv “hollow,” → concave.

Etymology (PE): Qafas “cage,” of unknown origin.

1. An enclosure, usually made with bars or wire, for keeping birds or wild animals.
   

2. An enclosed structure resembling a cage. → observer’s cage, → Faraday cage.

Etymology (EN): M.E. from O.Fr. cage, from L. cavea “hollow place, enclosure for animals,” cognate with Pers. kâv “hollow,” → concave.

Etymology (PE): Qafas “cage,” of unknown origin.

A member of a group of tiny (millimeter to centimeter) light-colored meteorites found often with → chondrules. They consist of high vaporization minerals, including → silicates and → oxides of Ca, Al, and Ti, but are quite poor in Fe. Compared to common → chondrules, which are uniformly spherical, their shapes are less regular. They appear to be 2-3 million years older than chondrules. CAI meteorites are probably the oldest solid materials to have formed in the → solar nebula.

See also: CAI, short for → Calcium, → Aluminium, and → Inclusion; → meteorite.

A member of a group of tiny (millimeter to centimeter) light-colored meteorites found often with → chondrules. They consist of high vaporization minerals, including → silicates and → oxides of Ca, Al, and Ti, but are quite poor in Fe. Compared to common → chondrules, which are uniformly spherical, their shapes are less regular. They appear to be 2-3 million years older than chondrules. CAI meteorites are probably the oldest solid materials to have formed in the → solar nebula.

See also: CAI, short for → Calcium, → Aluminium, and → Inclusion; → meteorite.

The standard model of → radiation-driven winds in which the acceleration of → stellar wind is provided by the → absorption and → scattering of ultraviolet photons in ions of abundant elements (→ CNO, → iron peak) in the → Lyman continuum. The model was developed by Castor et al. (1975), who assumed that the forces due to the radiative lines and the pressure gradients are functions of local velocity gradient, and used a large number (~ 10⁵) of lines which have a statistical distribution in line strengths. The model led to predictions of → mass loss rates (M_dot) and terminal velocities as a function of stellar properties and the line statistics parameters. With the modifications by Friend and Abbott (1986), Pauldrach et al. (1986), and Kudritzki et al. (1989), CAK multi-line theory gives good agreement with observationally derived values of mass loss rate and → terminal velocity (v_∞). CAK wind solutions predict the terminal velocity to be proportional to the → escape velocity and the mass loss rate to depend strongly on the stellar → luminosity. Observations over the past decades have shown that these main wind parameters, M_dot and v_∞, indeed behave as predicted by CAK. This basic agreement between observations and theory provides strong evidence that the winds from → massive stars are driven by → radiation pressure and this has favored the CAK formalism. See also → multiple scattering. See the review by J. Puls et al. 2008, Astron. Astrophys. Rev. 16, 209.

See also: CAK, the initials of the researchers who developed the model: J.I. Castor, D.C. Abbott, and R.I. Klein(1975, Radiation-driven winds in Of stars, ApJ 195, 157); → model.

The standard model of → radiation-driven winds in which the acceleration of → stellar wind is provided by the → absorption and → scattering of ultraviolet photons in ions of abundant elements (→ CNO, → iron peak) in the → Lyman continuum. The model was developed by Castor et al. (1975), who assumed that the forces due to the radiative lines and the pressure gradients are functions of local velocity gradient, and used a large number (~ 10⁵) of lines which have a statistical distribution in line strengths. The model led to predictions of → mass loss rates (M_dot) and terminal velocities as a function of stellar properties and the line statistics parameters. With the modifications by Friend and Abbott (1986), Pauldrach et al. (1986), and Kudritzki et al. (1989), CAK multi-line theory gives good agreement with observationally derived values of mass loss rate and → terminal velocity (v_∞). CAK wind solutions predict the terminal velocity to be proportional to the → escape velocity and the mass loss rate to depend strongly on the stellar → luminosity. Observations over the past decades have shown that these main wind parameters, M_dot and v_∞, indeed behave as predicted by CAK. This basic agreement between observations and theory provides strong evidence that the winds from → massive stars are driven by → radiation pressure and this has favored the CAK formalism. See also → multiple scattering. See the review by J. Puls et al. 2008, Astron. Astrophys. Rev. 16, 209.

See also: CAK, the initials of the researchers who developed the model: J.I. Castor, D.C. Abbott, and R.I. Klein(1975, Radiation-driven winds in Of stars, ApJ 195, 157); → model.

A → bipolar nebula and → OH/IR source with technical designation OH 231.8+4.2. It is a → proto-planetary nebula (PPN) 1.4 → light-years long and located some 5,000 light-years from Earth in the constellation → Puppis.

The obscured → central star, named QX Pup, is classified as M9-10 III and has a → Mira-like variability consistent with an evolved → asymptotic giant branch (AGB) star. The late evolution of this object may have been complex since it has a binary → companion star (of type A0 V) that has been indirectly identified from analysis of the spectrum of the hidden central source reflected by the nebular dust. The system has a total luminosity of ~ 10⁴ Lsun and its systemic velocity relative to the → Local Standard of Rest is V_LSR ~ 34 km s^-1. OH 231.8+4.2 is very likely a member of the → open cluster M46 with a progenitor mass of ~ 3 Msun. The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg (see, e.g., Prieto et al., 2015, A&A, 575, A84).

See also: The name “Calabash Nebula” was first proposed by Icke & Preston, 1989, A&A, 211, 409. It refers to the apparent form of the object which resembles a calabash “a tree that has large, rounded gourdlike fruit; the fruit of any of these plants,” from Sp. calabaza, possibly from Ar. qar’ah yâbisah “dry gourd,” from Pers. kharabuz, used of various large melons; → nebula.

A → bipolar nebula and → OH/IR source with technical designation OH 231.8+4.2. It is a → proto-planetary nebula (PPN) 1.4 → light-years long and located some 5,000 light-years from Earth in the constellation → Puppis.

The obscured → central star, named QX Pup, is classified as M9-10 III and has a → Mira-like variability consistent with an evolved → asymptotic giant branch (AGB) star. The late evolution of this object may have been complex since it has a binary → companion star (of type A0 V) that has been indirectly identified from analysis of the spectrum of the hidden central source reflected by the nebular dust. The system has a total luminosity of ~ 10⁴ Lsun and its systemic velocity relative to the → Local Standard of Rest is V_LSR ~ 34 km s^-1. OH 231.8+4.2 is very likely a member of the → open cluster M46 with a progenitor mass of ~ 3 Msun. The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg (see, e.g., Prieto et al., 2015, A&A, 575, A84).

See also: The name “Calabash Nebula” was first proposed by Icke & Preston, 1989, A&A, 211, 409. It refers to the apparent form of the object which resembles a calabash “a tree that has large, rounded gourdlike fruit; the fruit of any of these plants,” from Sp. calabaza, possibly from Ar. qar’ah yâbisah “dry gourd,” from Pers. kharabuz, used of various large melons; → nebula.

A metallic chemical element; symbol Ca. → Atomic number 20; → atomic weight 40.08; → melting point about 839°C; → boiling point 1,484°C; → specific gravity 1.55 at 20°C; → valence +2. It is fifth in abundance in the Earth’s crust, of which it forms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells. Never found in nature uncombined, it occurs abundantly as limestone, gypsum, and fluorite. Calcium has several radioactive isotopes. It was first isolated by the British chemist Humphry Davy in 1808.

See also: Coined by Sir Humphry Davy from L. calx (genitive calcis) “lime (CaO) or limestone (CaCO₃)” in which it was found, from Gk. khalix “small pebble,” see also → calculate, + → -ium.

A metallic chemical element; symbol Ca. → Atomic number 20; → atomic weight 40.08; → melting point about 839°C; → boiling point 1,484°C; → specific gravity 1.55 at 20°C; → valence +2. It is fifth in abundance in the Earth’s crust, of which it forms more than 3%. It is an essential constituent of leaves, bones, teeth, and shells. Never found in nature uncombined, it occurs abundantly as limestone, gypsum, and fluorite. Calcium has several radioactive isotopes. It was first isolated by the British chemist Humphry Davy in 1808.

See also: Coined by Sir Humphry Davy from L. calx (genitive calcis) “lime (CaO) or limestone (CaCO₃)” in which it was found, from Gk. khalix “small pebble,” see also → calculate, + → -ium.

A discontinuity in the spectrum of galaxies near the Ca II → H and K lines at about 4000 Å. The Ca break
is the most prominent feature in the spectra of elliptical galaxies. Its strength is given by the → calcium break index.

See also: → calcium; → break.

A discontinuity in the spectrum of galaxies near the Ca II → H and K lines at about 4000 Å. The Ca break
is the most prominent feature in the spectra of elliptical galaxies. Its strength is given by the → calcium break index.

See also: → calcium; → break.

The strength of the → calcium break, as measured from the fluxes in the intervals 3750-3950 Å and 4050-4250 Å. It is given by the expression Ca-break[%] = 100 · (f_upper - f_lower)/f_upper,
where f_upper and f_lower are the mean fluxes measured in the 3750-3950 Å and 4050-4250 Å bands, respectively,
in the rest frame
(Dressler & Shectman 1987, AJ 94, 899).

See also: → calcium; → break; → index.

The strength of the → calcium break, as measured from the fluxes in the intervals 3750-3950 Å and 4050-4250 Å. It is given by the expression Ca-break[%] = 100 · (f_upper - f_lower)/f_upper,
where f_upper and f_lower are the mean fluxes measured in the 3750-3950 Å and 4050-4250 Å bands, respectively,
in the rest frame
(Dressler & Shectman 1987, AJ 94, 899).

See also: → calcium; → break; → index.

To perform a mathematical process; to reckon; to make an estimate of; evaluate. → compute; → count; → mathematics; → statistics.

Etymology (EN): Calculate, from L.L. calculare, calculat-, from L. calculus “small stone, pebble” (used in reckoning), dim. of calx, calc- “limestone,” from Gk. khalix “small pebble,” kakhlex “round pebble,“cf. O.E. hægl, hagol “hale,”
from W.Gmc. *haglaz, O.H.G. hagal, O.N. hagl, Ger. Hagel “hail”, PIE *kaghlo- “pebble, hail.” The Pers. cognate is probably the Lori hogela “big stone.”

Etymology (PE): Afmârdan, from prefix af- + stem mar- + infinitive suffix -idan. The Mod.Pers. prefix af- “to, up, upon,” occurring in several words (e.g. afzudan, afruxtan, afsar, afsâr, afqân), derives from O.Pers./Av. abiy-/aiwi- “to, upon, against;” cf. Skt. abhi-, Gk. amphi-. The stem mar-, mâr- “count, reckon, measure,” which occurs in several Mid./Mod.Pers. terms (e.g. ošmârdan, šomârdan, šomordan “to count, to calculate,” âmâr “computation, arithmetic; statistics,” âmârdan “to reckon, to calculate,” bimar “countless,” nahmâr “great, large, big”), is related to the Av. base mar- “to have in mind, remember, recall,” hišmar-; cf.
Skt. smr-, smarati “to remember, he remembers,” L. memor, memoria, Gk. mermera “care,” martyr “witness.”

To perform a mathematical process; to reckon; to make an estimate of; evaluate. → compute; → count; → mathematics; → statistics.

Etymology (EN): Calculate, from L.L. calculare, calculat-, from L. calculus “small stone, pebble” (used in reckoning), dim. of calx, calc- “limestone,” from Gk. khalix “small pebble,” kakhlex “round pebble,“cf. O.E. hægl, hagol “hale,”
from W.Gmc. *haglaz, O.H.G. hagal, O.N. hagl, Ger. Hagel “hail”, PIE *kaghlo- “pebble, hail.” The Pers. cognate is probably the Lori hogela “big stone.”

Etymology (PE): Afmârdan, from prefix af- + stem mar- + infinitive suffix -idan. The Mod.Pers. prefix af- “to, up, upon,” occurring in several words (e.g. afzudan, afruxtan, afsar, afsâr, afqân), derives from O.Pers./Av. abiy-/aiwi- “to, upon, against;” cf. Skt. abhi-, Gk. amphi-. The stem mar-, mâr- “count, reckon, measure,” which occurs in several Mid./Mod.Pers. terms (e.g. ošmârdan, šomârdan, šomordan “to count, to calculate,” âmâr “computation, arithmetic; statistics,” âmârdan “to reckon, to calculate,” bimar “countless,” nahmâr “great, large, big”), is related to the Av. base mar- “to have in mind, remember, recall,” hišmar-; cf.
Skt. smr-, smarati “to remember, he remembers,” L. memor, memoria, Gk. mermera “care,” martyr “witness.”

The act, process, or result of calculating.

Etymology (EN): Calculation, noun from → calculate.

Etymology (PE): Afmâreš, verbal noun from afmârdan→ calculate.

The act, process, or result of calculating.

Etymology (EN): Calculation, noun from → calculate.

Etymology (PE): Afmâreš, verbal noun from afmârdan→ calculate.

A small electronic device that performs calculations.

Etymology (EN): Calculator, from → calculate + → -tor.

Etymology (PE): Afmârgar, from afmâr→ calculate + -gar agent suffix, from kar-, kardan “to do, to make” (Mid.Pers. kardan, O.Pers./Av. kar- “to do, make, build,” Av. kərənaoiti “makes,” cf. Skt. kr- “to do, to make,” krnoti “makes,” karma “act, deed;” PIE base k^wer- “to do, to make”).

A small electronic device that performs calculations.

Etymology (EN): Calculator, from → calculate + → -tor.

Etymology (PE): Afmârgar, from afmâr→ calculate + -gar agent suffix, from kar-, kardan “to do, to make” (Mid.Pers. kardan, O.Pers./Av. kar- “to do, make, build,” Av. kərənaoiti “makes,” cf. Skt. kr- “to do, to make,” krnoti “makes,” karma “act, deed;” PIE base k^wer- “to do, to make”).

The branch of mathematics that deals with limits and the → differentiation and → integration of → functions of one or more → variables. Same as → infinitesimal calculus and → differential calculus .

Etymology (EN): L. calculus “small stone,” from calx, calcis “limestone,” → calculate, + -ulus diminutive suffix, → -ule.

Etymology (PE): Afmârik, from afmâr, → calculate

• Pers. suffix -ik denoting a subject, a branch of sciences, a discipline, → ics.

The branch of mathematics that deals with limits and the → differentiation and → integration of → functions of one or more → variables. Same as → infinitesimal calculus and → differential calculus .

Etymology (EN): L. calculus “small stone,” from calx, calcis “limestone,” → calculate, + -ulus diminutive suffix, → -ule.

Etymology (PE): Afmârik, from afmâr, → calculate

• Pers. suffix -ik denoting a subject, a branch of sciences, a discipline, → ics.

A → claculus based on the properties of the successive values of → variable quantities and their → differences or → increments.

Etymology (EN): → calculus, → finite, → difference.

Etymology (PE): Afmârik, → calculus, degarsânihâ, plural of degarsân, → difference, karânmand,
→ finite.

A → claculus based on the properties of the successive values of → variable quantities and their → differences or → increments.

Etymology (EN): → calculus, → finite, → difference.

Etymology (PE): Afmârik, → calculus, degarsânihâ, plural of degarsân, → difference, karânmand,
→ finite.

A branch of mathematics that deals with the calculation of the probabilities of events.

Etymology (EN): → calculus; → probability.

Etymology (PE): Afmârik, → calculus; šavânâihâ, plural of šavânâi→ probability.

A branch of mathematics that deals with the calculation of the probabilities of events.

Etymology (EN): → calculus; → probability.

Etymology (PE): Afmârik, → calculus; šavânâihâ, plural of šavânâi→ probability.

The application of → Cauchy’s theorem to compute residues and poles, evaluate contour integrals, sum infinite series, and carry out related calculations.

See also: → calculus; → residue.

The application of → Cauchy’s theorem to compute residues and poles, evaluate contour integrals, sum infinite series, and carry out related calculations.

See also: → calculus; → residue.

The branch of mathematics dealing with the differentiation of tensors.

Etymology (EN): → calculus; → tensor.

Etymology (PE): Afmârik, → calculus; → tensor.

The branch of mathematics dealing with the differentiation of tensors.

Etymology (EN): → calculus; → tensor.

Etymology (PE): Afmârik, → calculus; → tensor.

The study of maximum and minimum properties of → definite integrals.

Etymology (EN): → calculus; → variation.

Etymology (PE): Afmârik, → calculus; varteš→ variation.

The study of maximum and minimum properties of → definite integrals.

Etymology (EN): → calculus; → variation.

Etymology (PE): Afmârik, → calculus; varteš→ variation.

The area of calculus dealing with differentiation and integration of vector-valued functions; a sub-area of tensor calculus.

Etymology (EN): → calculus; → vector.

Etymology (PE): Afmârik, → calculus;
bordâr, → vector.

The area of calculus dealing with differentiation and integration of vector-valued functions; a sub-area of tensor calculus.

Etymology (EN): → calculus; → vector.

Etymology (PE): Afmârik, → calculus;
bordâr, → vector.

A large, roughly circular, → crater with diameter at least three or four times depth on the summit or in the side of a → volcano. A caldera can form from a volcanic blast or the collapse of a volcanic cone into an emptied → magma chamber.

Etymology (EN): From Sp. caldera “cauldron, kettle,” also name of a crater on Canary Islands, from L. caldarius “of warming,” from calidus “warm, hot,” → calorie.

Etymology (PE): Tiyân “large cauldron; cauldron used for warming water in a communal bathhouse,” of unknown origin.

A large, roughly circular, → crater with diameter at least three or four times depth on the summit or in the side of a → volcano. A caldera can form from a volcanic blast or the collapse of a volcanic cone into an emptied → magma chamber.

Etymology (EN): From Sp. caldera “cauldron, kettle,” also name of a crater on Canary Islands, from L. caldarius “of warming,” from calidus “warm, hot,” → calorie.

Etymology (PE): Tiyân “large cauldron; cauldron used for warming water in a communal bathhouse,” of unknown origin.

A collection of 109 impressive celestial objects compiled for amateur astronomers. These objects (→ star clusters, → nebulae, → supernova remnants, and → galaxies), selected from the → New General Catalog and the → Index Catalog, are not present in the → Messier catalog.

See also: Named after Patrick Caldwell Moore (1923-2012), English amateur astronomer, who compiled the catalog in 1995; → catalog.

A collection of 109 impressive celestial objects compiled for amateur astronomers. These objects (→ star clusters, → nebulae, → supernova remnants, and → galaxies), selected from the → New General Catalog and the → Index Catalog, are not present in the → Messier catalog.

See also: Named after Patrick Caldwell Moore (1923-2012), English amateur astronomer, who compiled the catalog in 1995; → catalog.

1. Any of various systems for measuring and recording the passage of time by dividing the year into days, weeks, and months.
   
2. A table showing the months, weeks, and days in at least one specific year.
   → chronology.

Etymology (EN): M.E. calender, from O.Fr. calendier, from L. calendarium “account book,” from kalendae “calends” the first day of the Roman month,
from calare “to announce solemnly, call out,” as the priests did in proclaiming the new moon that marked the calends, from PIE base *kele- “to call, shout” (cf. Skt. usakala “cock,” lit. “dawn-calling;” Gk. kaleo “to call,” kelados “noise,” kledon “report, fame;” O.H.G. halan, O.N. kalla “to call;” O.E. hlowan “to low;” Lith. kalba “language”).

Etymology (PE): Gâhšomâr, gâhšomâri, gâhmâr from gâh “time,” Mid.Pers. gâh, gâs,

• šomâr, mâr “reckoning,” → calculate.
  Sâlnâmé, from sâl, → year, + nâmé “a writing, letter, book.”

1. Any of various systems for measuring and recording the passage of time by dividing the year into days, weeks, and months.
   
2. A table showing the months, weeks, and days in at least one specific year.
   → chronology.

Etymology (EN): M.E. calender, from O.Fr. calendier, from L. calendarium “account book,” from kalendae “calends” the first day of the Roman month,
from calare “to announce solemnly, call out,” as the priests did in proclaiming the new moon that marked the calends, from PIE base *kele- “to call, shout” (cf. Skt. usakala “cock,” lit. “dawn-calling;” Gk. kaleo “to call,” kelados “noise,” kledon “report, fame;” O.H.G. halan, O.N. kalla “to call;” O.E. hlowan “to low;” Lith. kalba “language”).

Etymology (PE): Gâhšomâr, gâhšomâri, gâhmâr from gâh “time,” Mid.Pers. gâh, gâs,

• šomâr, mâr “reckoning,” → calculate.
  Sâlnâmé, from sâl, → year, + nâmé “a writing, letter, book.”

A period of 24 hours, from one midnight to the following midnight.

See also: → calendar; → day.

A period of 24 hours, from one midnight to the following midnight.

See also: → calendar; → day.

One of the periods into which a calendar is divided, ordinarily 12, but in earlier systems 10 (the first Roman calendar under Romulus) or 13 (ancient Iranian calendar using a month intercalation).

See also: → calendar; → month.

One of the periods into which a calendar is divided, ordinarily 12, but in earlier systems 10 (the first Roman calendar under Romulus) or 13 (ancient Iranian calendar using a month intercalation).

See also: → calendar; → month.

The time interval between the new year’s day in a given calendar system and the day before the following new year’s day. In the Gregorian system the calendar year begins on January 1 and ends on December 31. In the Iranian calendar it begins on Farvardin 1, the day closest to the spring equinox and ends on Esfand 29 or 30.

See also: → calendar; → year.

The time interval between the new year’s day in a given calendar system and the day before the following new year’s day. In the Gregorian system the calendar year begins on January 1 and ends on December 31. In the Iranian calendar it begins on Farvardin 1, the day closest to the spring equinox and ends on Esfand 29 or 30.

See also: → calendar; → year.

1. Young of a bovine animal. See also → calve, → glacier calving.
   

   2. The fleshy part of a person’s → leg below the → knee.

Etymology (EN): M.E., from O.E. cealf, calf, cognate with M.Du. calf, Ger. Kalb, Gothic kalbo.

Etymology (PE): 1) Gug (Dehxodâ), variant gog “calf;” probably from Proto-Ir. *gao-ka “baby cow, little caow,” from *gao- “cow, bull,” → cow, + suffix -*ak.
Gusâlé, literally “young in years,” from gu, → cow, + sâl, → year.

2. Poviz, from Laki poviz “calf,” may be ultimately from *povik, from *pov variant of pâ “leg, → foot” + suffix-ik, → -ics; cf. Ilâmi, Nahâvandi piz “the leg calf.”

1. Young of a bovine animal. See also → calve, → glacier calving.
   

   2. The fleshy part of a person’s → leg below the → knee.

Etymology (EN): M.E., from O.E. cealf, calf, cognate with M.Du. calf, Ger. Kalb, Gothic kalbo.

Etymology (PE): 1) Gug (Dehxodâ), variant gog “calf;” probably from Proto-Ir. *gao-ka “baby cow, little caow,” from *gao- “cow, bull,” → cow, + suffix -*ak.
Gusâlé, literally “young in years,” from gu, → cow, + sâl, → year.

2. Poviz, from Laki poviz “calf,” may be ultimately from *povik, from *pov variant of pâ “leg, → foot” + suffix-ik, → -ics; cf. Ilâmi, Nahâvandi piz “the leg calf.”

To adjust or determine, by comparison with a standard, the response magnitude of a measuring instrument as a function of the input signal. For example, to determine line wavelengths in the spectrum of an astronomical object, or to graduate a hygrometer.

Etymology (EN): From M.Fr. calibre, via Sp. or It., from Ar. qalib “a mold, last,” perhaps from Gk. kalopodion “a shoemaker’s last,” from kalon “wood” + podos gen. of pous “foot.”

Etymology (PE): Kabizidan, verbal form of kabiz (varianats kaviz, kaviž, kafiz) “a measure for grain, a bushel,” from Mid.Pers. kabiz “a grain measure,” loaned in Arm. kapic “a grain measure,” and in Gk. kapithe, as attested in Xenophon.

To adjust or determine, by comparison with a standard, the response magnitude of a measuring instrument as a function of the input signal. For example, to determine line wavelengths in the spectrum of an astronomical object, or to graduate a hygrometer.

Etymology (EN): From M.Fr. calibre, via Sp. or It., from Ar. qalib “a mold, last,” perhaps from Gk. kalopodion “a shoemaker’s last,” from kalon “wood” + podos gen. of pous “foot.”

Etymology (PE): Kabizidan, verbal form of kabiz (varianats kaviz, kaviž, kafiz) “a measure for grain, a bushel,” from Mid.Pers. kabiz “a grain measure,” loaned in Arm. kapic “a grain measure,” and in Gk. kapithe, as attested in Xenophon.

1. The act or process of calibrating or the state of being calibrated.
   
2. A set of graduations that show positions or values.

Etymology (EN): Calibration, noun from → calibrate.

Etymology (PE): Kabizeš, noun from kabizidan, → calibrate.

1. The act or process of calibrating or the state of being calibrated.
   
2. A set of graduations that show positions or values.

Etymology (EN): Calibration, noun from → calibrate.

Etymology (PE): Kabizeš, noun from kabizidan, → calibrate.

An empirical curve obtained through appropriate exposures in order to determine the instrument’s response. For example, a curve allowing the conversion of relative intensities of an observed object into absolute fluxes, or a curve relating the detector’s pixel positions to wavelengths.

See also: → calibration; → curve.

An empirical curve obtained through appropriate exposures in order to determine the instrument’s response. For example, a curve allowing the conversion of relative intensities of an observed object into absolute fluxes, or a curve relating the detector’s pixel positions to wavelengths.

See also: → calibration; → curve.

A systematic error in the constant values to be applied to a measuring instrument.

Etymology (EN): → calibration; → error.

Etymology (PE): Irang, → error;
kabizeš, → calibration.

A systematic error in the constant values to be applied to a measuring instrument.

Etymology (EN): → calibration; → error.

Etymology (PE): Irang, → error;
kabizeš, → calibration.

An exposure obtained with an instrument mounted on the telescope using an artificial illuminating source in order to calibrate the instrument.

Etymology (EN): → calibration; → exposure.

Etymology (PE): Nurdâd, → exposure; kabizeš, → calibration.

An exposure obtained with an instrument mounted on the telescope using an artificial illuminating source in order to calibrate the instrument.

Etymology (EN): → calibration; → exposure.

Etymology (PE): Nurdâd, → exposure; kabizeš, → calibration.

A lamp used for instrument calibration, such as an internal He-Ar arc for wavelength calibration or an external source of light placed in the telescope dome for flat-field exposures.

Etymology (EN): → calibration; lamp, from O.Fr. lampe, L. lampas, from Gk. lampas “torch, lamp, light, meteor,” from lampein “to shine.”

Etymology (PE): Kabizeš, → calibration; lâmp, from Fr., as above.

A lamp used for instrument calibration, such as an internal He-Ar arc for wavelength calibration or an external source of light placed in the telescope dome for flat-field exposures.

Etymology (EN): → calibration; lamp, from O.Fr. lampe, L. lampas, from Gk. lampas “torch, lamp, light, meteor,” from lampein “to shine.”

Etymology (PE): Kabizeš, → calibration; lâmp, from Fr., as above.

A general term for certain reference astronomical sources that allow determining the characteristics (magnitude, distance, velocity, etc.) of other sources. → primary calibrators, → secondary calibrators.

Etymology (EN): Calibrator, from → calibrate + → -or.

Etymology (PE): Kabizandé, agent noun from kabizidan, → calibrate.

A general term for certain reference astronomical sources that allow determining the characteristics (magnitude, distance, velocity, etc.) of other sources. → primary calibrators, → secondary calibrators.

Etymology (EN): Calibrator, from → calibrate + → -or.

Etymology (PE): Kabizandé, agent noun from kabizidan, → calibrate.

1a) To cry out in a loud voice; shout.

1b) To command or request to come; summon.

1c) To speak loudly, as to attract attention; shout; cry.

2) To name or address (someone) as.  <BR>

3a) A cry or shout.

3b) The cry or vocal sound of a bird or other animal (Dictionary.com)

Etymology (EN): M.E. callen, from O.Norse kalla “to call out,” cognate with M.Du. kallen “to talk,” O.H.G. kallon “to shout,” akin to O.E. -calla “herald,” Irish gall “swan,” O.C.S. glasu “voice”.

Etymology (PE): Žâridan, from žâr, from Oroshori (or Roshorvi) žâr-/žart- “to sound, ring,” cognate with Parachi jâr “to say,” Ossetic gær, qær “noise, shout,” other cognates in Per. âžir “cry, call”, qâl, qil “noise, brouhaha,” jâr “cry, call”, žaqâr, zaqâr “cry, call”, payqâre “blame, reproval,” gerâmi “dear, beloved,” ultimately from Proto-Ir. *uz-garH-, from *garH- “to call, greet,” which has also given rise to Av. âγar- “to greet,” akin to Skt. garⁱ “to praise, welcome;” L. gratis “welcome;” PIE root g^werH- “to praise, to say.”

1a) To cry out in a loud voice; shout.

1b) To command or request to come; summon.

1c) To speak loudly, as to attract attention; shout; cry.

2) To name or address (someone) as.  <BR>

3a) A cry or shout.

3b) The cry or vocal sound of a bird or other animal (Dictionary.com)

Etymology (EN): M.E. callen, from O.Norse kalla “to call out,” cognate with M.Du. kallen “to talk,” O.H.G. kallon “to shout,” akin to O.E. -calla “herald,” Irish gall “swan,” O.C.S. glasu “voice”.

Etymology (PE): Žâridan, from žâr, from Oroshori (or Roshorvi) žâr-/žart- “to sound, ring,” cognate with Parachi jâr “to say,” Ossetic gær, qær “noise, shout,” other cognates in Per. âžir “cry, call”, qâl, qil “noise, brouhaha,” jâr “cry, call”, žaqâr, zaqâr “cry, call”, payqâre “blame, reproval,” gerâmi “dear, beloved,” ultimately from Proto-Ir. *uz-garH-, from *garH- “to call, greet,” which has also given rise to Av. âγar- “to greet,” akin to Skt. garⁱ “to praise, welcome;” L. gratis “welcome;” PIE root g^werH- “to praise, to say.”

A period of 76 years after which the new and full moons would return to the same day of the solar year. This was intended as an improvement of the → Metonic cycle because the 6940 days of the Metonic cycle exceeded 19 years by about a quarter of a day, and exceeded 235 → lunations by a larger amount of time.

See also: Named after Calippus of Cyzicus (about 370-300 BC), a Greek astronomer and mathematician.

A period of 76 years after which the new and full moons would return to the same day of the solar year. This was intended as an improvement of the → Metonic cycle because the 6940 days of the Metonic cycle exceeded 19 years by about a quarter of a day, and exceeded 235 → lunations by a larger amount of time.

See also: Named after Calippus of Cyzicus (about 370-300 BC), a Greek astronomer and mathematician.

The eighth of → Jupiter’s known moons and the second brightest and the outermost of the four → Galilean satellites. With a diameter of 4800 km (0.38 Earths), Castillo is roughly the same size as Mercury. It orbits Jupiter in 16.689 days at a distance of 1,883,000 km from the planet, beyond Jupiter’s main → radiation belts. It is the third largest moon in the entire solar system. Its mass is 10.76 × 10²² kg (about 1.5 Earth Moons) and its mean → surface temperature is -155 °C. The most prominent feature of Callisto is its craters, as it has the most craters of any object in the solar system. Due to its orbit being further away from Jupiter, it is not under the same → tidal heating influences as → Io, → Europa, or → Ganymede.

Callisto’s thin → atmosphere is composed of → carbon dioxide and likely some → molecular oxygen. Callisto is thought to have formed as a result of slow → accretion from the → protoplanetary disk of gas and dust that surrounded Jupiter after its formation.

Etymology (EN): Callisto, an attendant of Artemis in Greek mythology. Because of her love affair with Zeus, she was transformed into a bear by Artemis. According to another legend she was changed into a bear by the jealous Hera. Zeus transferred her to the heavens as the → constellation  → Ursa Major (great bear).

The eighth of → Jupiter’s known moons and the second brightest and the outermost of the four → Galilean satellites. With a diameter of 4800 km (0.38 Earths), Castillo is roughly the same size as Mercury. It orbits Jupiter in 16.689 days at a distance of 1,883,000 km from the planet, beyond Jupiter’s main → radiation belts. It is the third largest moon in the entire solar system. Its mass is 10.76 × 10²² kg (about 1.5 Earth Moons) and its mean → surface temperature is -155 °C. The most prominent feature of Callisto is its craters, as it has the most craters of any object in the solar system. Due to its orbit being further away from Jupiter, it is not under the same → tidal heating influences as → Io, → Europa, or → Ganymede.

Callisto’s thin → atmosphere is composed of → carbon dioxide and likely some → molecular oxygen. Callisto is thought to have formed as a result of slow → accretion from the → protoplanetary disk of gas and dust that surrounded Jupiter after its formation.

Etymology (EN): Callisto, an attendant of Artemis in Greek mythology. Because of her love affair with Zeus, she was transformed into a bear by Artemis. According to another legend she was changed into a bear by the jealous Hera. Zeus transferred her to the heavens as the → constellation  → Ursa Major (great bear).

1. Thermodynamics: The amount of → heat, in the → CGS system, required to raise the temperature of one gram of water from 14.5 °C to 15.5 °C at standard pressure. It is equal
   to 4.1858 → joules, a quantity called the 15° calorie. Also called gram-calorie, small calorie.
   

2. Physiology: A unit used to express the heat output of an organism and the fuel or energy value of food. It is equal to one kilocalorie.

See also: From Fr. calorie, from L. calor “heat,” calidus “warm;” PIE base *kelə- “cold; warm;”
Av. sarəta- “cold;” Mod.Pers. sard “cold, cool;” Skt. śiśira- “cold;”
Ossetian sald “cold,” Lith. šaltas “cold,”
silti “become warm;” Welsh clyd “cool.”

1. Thermodynamics: The amount of → heat, in the → CGS system, required to raise the temperature of one gram of water from 14.5 °C to 15.5 °C at standard pressure. It is equal
   to 4.1858 → joules, a quantity called the 15° calorie. Also called gram-calorie, small calorie.
   

2. Physiology: A unit used to express the heat output of an organism and the fuel or energy value of food. It is equal to one kilocalorie.

See also: From Fr. calorie, from L. calor “heat,” calidus “warm;” PIE base *kelə- “cold; warm;”
Av. sarəta- “cold;” Mod.Pers. sard “cold, cool;” Skt. śiśira- “cold;”
Ossetian sald “cold,” Lith. šaltas “cold,”
silti “become warm;” Welsh clyd “cool.”

The measurement of the amount of → heat involved in various processes, such as chemical reactions, changes of state, and formation of solutions.

Etymology (EN): From L. calori- “heat,” combining form of calor, → calorie, + → -metry.

Etymology (PE): Garmâsanji, from garmâ  → heat

• -sanji  → -metry.

The measurement of the amount of → heat involved in various processes, such as chemical reactions, changes of state, and formation of solutions.

Etymology (EN): From L. calori- “heat,” combining form of calor, → calorie, + → -metry.

Etymology (PE): Garmâsanji, from garmâ  → heat

• -sanji  → -metry.

1. To give birth to a calf.
   

   2. Of a → glacier, to break off
      so as to give birth to an → iceberg. → glacier calving.

Etymology (EN): M.E. calven, O.E. (Anglian) *calfian, from → calf.

Etymology (PE): Gugidan, infinitive from gug “cow, bull,” → cow.

1. To give birth to a calf.
   

   2. Of a → glacier, to break off
      so as to give birth to an → iceberg. → glacier calving.

Etymology (EN): M.E. calven, O.E. (Anglian) *calfian, from → calf.

Etymology (PE): Gugidan, infinitive from gug “cow, bull,” → cow.

A satellite of Saturn discovered in 1980 on the images taken by Voyager 1. It shares the same orbit as Telesto and Tethys at a distance of 294,660 km and turns around the planet with a period of 1.888 days. It is 34 x 22 x 22 km in size.

Etymology (EN): In Greek mythology, Calypso was a sea nymph and the daughter of the Titan Atlas.

A satellite of Saturn discovered in 1980 on the images taken by Voyager 1. It shares the same orbit as Telesto and Tethys at a distance of 294,660 km and turns around the planet with a period of 1.888 days. It is 34 x 22 x 22 km in size.

Etymology (EN): In Greek mythology, Calypso was a sea nymph and the daughter of the Titan Atlas.

The Giraffe. An extended but inconspicuous
→ constellation near the north celestial pole. Approximate position: R.A. 5 h, Dec. 70°; abbreviation Cam, genitive form Camelopardalis.

Etymology (EN): M.E., from Medieval L. camlopardus, from L. camelopardalis, from Gk. kamelopardalis, from kamelos “camel” + pardalis, pard “leopard” (because the giraffe has a head like a camel’s and the spots of a leopard), from L. pardus, from Gk. pardos “male panther,” from the same source (probably Iranian) as Skt. prdaku- “leopard, tiger, snake,” and Pers. palang “panther.”

Etymology (PE): Zarrâfé “giraffe,” from Ar. zarafa, probably from an African language. This term is at the origin of
this animal’s name in European languages, via
It. giraffa. The Pers. name of the animal is: šotor-gâv-palang, from Mid.Pers., composed of šotor “camel” + gâv “ox, bull, cow,” → Taurus, + palang “panther.”

The Giraffe. An extended but inconspicuous
→ constellation near the north celestial pole. Approximate position: R.A. 5 h, Dec. 70°; abbreviation Cam, genitive form Camelopardalis.

Etymology (EN): M.E., from Medieval L. camlopardus, from L. camelopardalis, from Gk. kamelopardalis, from kamelos “camel” + pardalis, pard “leopard” (because the giraffe has a head like a camel’s and the spots of a leopard), from L. pardus, from Gk. pardos “male panther,” from the same source (probably Iranian) as Skt. prdaku- “leopard, tiger, snake,” and Pers. palang “panther.”

Etymology (PE): Zarrâfé “giraffe,” from Ar. zarafa, probably from an African language. This term is at the origin of
this animal’s name in European languages, via
It. giraffa. The Pers. name of the animal is: šotor-gâv-palang, from Mid.Pers., composed of šotor “camel” + gâv “ox, bull, cow,” → Taurus, + palang “panther.”

1. An apparatus for recording the light from an object onto a sensitive material, such as film or CCD detector.
   
2. A device that converts optical images into electrical impulses.

Etymology (EN): Mod.L. camera obscura “dark chamber” from L. camera “vaulted room,” from Gk. kamara “vault,” cf. Av. kamarâ- “waist; vault” Mod.Pers. kamar “waist,” Skt. kamarati “is vaulted;” PIE base *kam- “to arch.”

Etymology (PE): Kadak “small room,” from kad, kadé “room, chamber, habitation, vault, cell, cavern,” Mid.Pers. katak, Av. kata- “(small) room, closet, (small) house,” cf. Goth. hethjo “small room” O.S. kotici “cavern, nest,” PIE *kot(os).

1. An apparatus for recording the light from an object onto a sensitive material, such as film or CCD detector.
   
2. A device that converts optical images into electrical impulses.

Etymology (EN): Mod.L. camera obscura “dark chamber” from L. camera “vaulted room,” from Gk. kamara “vault,” cf. Av. kamarâ- “waist; vault” Mod.Pers. kamar “waist,” Skt. kamarati “is vaulted;” PIE base *kam- “to arch.”

Etymology (PE): Kadak “small room,” from kad, kadé “room, chamber, habitation, vault, cell, cavern,” Mid.Pers. katak, Av. kata- “(small) room, closet, (small) house,” cf. Goth. hethjo “small room” O.S. kotici “cavern, nest,” PIE *kot(os).

A 3.6 m optical/infrared telescope jointly owned and operated by the Canadian National Research Council (NRC), the French Centre National de la Recherche Scientifique (CNRS), and the University of Hawaii. It became operational in 1979. The observatory is located atop the summit of Mauna Kea, a 4200 m, dormant volcano located on the island of Hawaii.

The Observatory headquarters is located in Waimea (also known as Kamuela by the US Postal Service).

Situated at the low latitude of Hawaii (+19° 45’), there is a fairly large sky overlapping with that of the → European Southern Observatory (ESO)  → La Silla observatory (δ = -29° 15’).

The point where an object is seen at the same → zenith distance from La Silla and from Mauna Kea, when it crosses the meridian, is δ =-5°. Taking into consideration also the difference in elevation between the observatories, the → declination at which one has equal air mass is moved down to δ =-18°. The extreme limit of observing from Mauna Kea is -60° (10° above horizon) but all programs below -20° are most efficiently carried out from ESO.

See also: Canada, from the St. Lawrence Iroquoian word kanata, meaning “village” or “settlement;”

France, from the L. Francia “country of the Franks;”

Hawaii, named for Hawai’iloa, a legendary figure from Hawaiian mytholgy;

→ telescope.

A 3.6 m optical/infrared telescope jointly owned and operated by the Canadian National Research Council (NRC), the French Centre National de la Recherche Scientifique (CNRS), and the University of Hawaii. It became operational in 1979. The observatory is located atop the summit of Mauna Kea, a 4200 m, dormant volcano located on the island of Hawaii.

The Observatory headquarters is located in Waimea (also known as Kamuela by the US Postal Service).

Situated at the low latitude of Hawaii (+19° 45’), there is a fairly large sky overlapping with that of the → European Southern Observatory (ESO)  → La Silla observatory (δ = -29° 15’).

The point where an object is seen at the same → zenith distance from La Silla and from Mauna Kea, when it crosses the meridian, is δ =-5°. Taking into consideration also the difference in elevation between the observatories, the → declination at which one has equal air mass is moved down to δ =-18°. The extreme limit of observing from Mauna Kea is -60° (10° above horizon) but all programs below -20° are most efficiently carried out from ESO.

See also: Canada, from the St. Lawrence Iroquoian word kanata, meaning “village” or “settlement;”

France, from the L. Francia “country of the Franks;”

Hawaii, named for Hawai’iloa, a legendary figure from Hawaiian mytholgy;

→ telescope.

To make void; revoke; annul.

Etymology (EN): M.E. cancellen, from M.L. cancellare “to cross out,” from L.
cancellare “to make like a lattice,”
from cancelli “lattice, grating.”

Etymology (PE): Fâtaridan, from Sogd. fâtar “to remove, to set aside,” from *fra-taraya-, from *tar- “to cross” (Cheung 2007),
→ trans-.

To make void; revoke; annul.

Etymology (EN): M.E. cancellen, from M.L. cancellare “to cross out,” from L.
cancellare “to make like a lattice,”
from cancelli “lattice, grating.”

Etymology (PE): Fâtaridan, from Sogd. fâtar “to remove, to set aside,” from *fra-taraya-, from *tar- “to cross” (Cheung 2007),
→ trans-.

The Crab. The dimmest → constellation of the → Zodiac, located in the northern hemisphere at approximately R.A. 8 h and Dec. +20°. The main feature of the constellation is the open cluster → Praesepe (M 44). Abbreviation: Cnc; genitive form: Cancri.

Etymology (EN): Cancer,from L., from Gk. karkinos; PIE base *qarq- “to be hard” (like the shell of a crab); cf. Skt. karkatah “crab,” karkarah “hard."
In Gk. mythology the Crab was sent by the goddess Hera to bite Hercules in the midst of the struggle with → Hydra, but Hercules crushed the crustacean
with his heel. Hera rewarded the Crab by placing it in the → Zodiac.

Etymology (PE): Xarcang “crab,” from Mid.Pers. karcang, cf. Lori qerženg from kar-, qer- + cang, ženg “claw.” The component
xar/qer may be related to Av. xruta-, xraoždva- “hard,” as in xruždisma- “hard ground” (from xruždi-

• zam-), and to the PIE *qarq- “to be hard.” In that case, the Pers. term for crab would literally mean “hard claw.”

The Crab. The dimmest → constellation of the → Zodiac, located in the northern hemisphere at approximately R.A. 8 h and Dec. +20°. The main feature of the constellation is the open cluster → Praesepe (M 44). Abbreviation: Cnc; genitive form: Cancri.

Etymology (EN): Cancer,from L., from Gk. karkinos; PIE base *qarq- “to be hard” (like the shell of a crab); cf. Skt. karkatah “crab,” karkarah “hard."
In Gk. mythology the Crab was sent by the goddess Hera to bite Hercules in the midst of the struggle with → Hydra, but Hercules crushed the crustacean
with his heel. Hera rewarded the Crab by placing it in the → Zodiac.

Etymology (PE): Xarcang “crab,” from Mid.Pers. karcang, cf. Lori qerženg from kar-, qer- + cang, ženg “claw.” The component
xar/qer may be related to Av. xruta-, xraoždva- “hard,” as in xruždisma- “hard ground” (from xruždi-

• zam-), and to the PIE *qarq- “to be hard.” In that case, the Pers. term for crab would literally mean “hard claw.”

→ Tropic of Cancer.

→ Tropic of Cancer.

The → SI unit of → luminous intensity in a given direction; symbol cd. It is defined by taking the fixed numerical value of the → luminous efficacy of → monochromatic radiation of → frequency 540 × 10¹² Hz, K_cd, to be 683 when expressed in the unit lm W^-1, which is equal to cd sr W^-1, or cd sr kg^-1 m^-2 s³, where the kilogram, meter and second are defined in terms of → Planck’s constant (h), → velocity of light (c), and Δν_Cs.

See also: From L. candela, → candle.

The → SI unit of → luminous intensity in a given direction; symbol cd. It is defined by taking the fixed numerical value of the → luminous efficacy of → monochromatic radiation of → frequency 540 × 10¹² Hz, K_cd, to be 683 when expressed in the unit lm W^-1, which is equal to cd sr W^-1, or cd sr kg^-1 m^-2 s³, where the kilogram, meter and second are defined in terms of → Planck’s constant (h), → velocity of light (c), and Δν_Cs.

See also: From L. candela, → candle.

1. An applicant or suitable person for a position.
   

2. An astronomical entity which is being considered for belonging to a special class of entities; e.g. → black hole candidate, → dark matter candidate, → supernova candidate.

Etymology (EN): From L. candidatus “clothed in white” (reference to the white togas worn by those seeking office),
from candidus “shining white,” from candere “to shine,” cf. Skt. cand- “to shine,” candra “bright; the Moon;”
PIE base *kand- “to glow, to shine.”

Etymology (PE): Nâmzad, literally “nominated,” from nâm, → name,

• zad, p.p. of zadan “to strike” (Mid.Pers. zatan, žatan, O.Pers./Av. jan-, gan- “to strike, hit, smite, kill,”
  Skt. han- “to strike, beat,”
  Gk. theinein “to strike,” L. fendere “to strike, push,” Gmc *gundjo “war, battle;” PIE *g^when- “to strike, kill”).

1. An applicant or suitable person for a position.
   

2. An astronomical entity which is being considered for belonging to a special class of entities; e.g. → black hole candidate, → dark matter candidate, → supernova candidate.

Etymology (EN): From L. candidatus “clothed in white” (reference to the white togas worn by those seeking office),
from candidus “shining white,” from candere “to shine,” cf. Skt. cand- “to shine,” candra “bright; the Moon;”
PIE base *kand- “to glow, to shine.”

Etymology (PE): Nâmzad, literally “nominated,” from nâm, → name,

• zad, p.p. of zadan “to strike” (Mid.Pers. zatan, žatan, O.Pers./Av. jan-, gan- “to strike, hit, smite, kill,”
  Skt. han- “to strike, beat,”
  Gk. theinein “to strike,” L. fendere “to strike, push,” Gmc *gundjo “war, battle;” PIE *g^when- “to strike, kill”).

1. A cylinder or block of wax, tallow, or other fatty substance with a central wick, which is burned to produce light.
   

2. A unit of luminous intensity, superseded by the → candela.

Etymology (EN): M.E., O.E. candel, from L. candela “a light, torch,” from candere “to shine,” candidus “shining white” (E. candidate); cf. Skt. cand- “to shine, to glow,” candati “shines,” candra- “shining, glowing, the Moon;” Gk. kandaros “coal;” PIE base *kand- “to glow, to shine.”

Etymology (PE): Šam’, loan from Ar.

1. A cylinder or block of wax, tallow, or other fatty substance with a central wick, which is burned to produce light.
   

2. A unit of luminous intensity, superseded by the → candela.

Etymology (EN): M.E., O.E. candel, from L. candela “a light, torch,” from candere “to shine,” candidus “shining white” (E. candidate); cf. Skt. cand- “to shine, to glow,” candati “shines,” candra- “shining, glowing, the Moon;” Gk. kandaros “coal;” PIE base *kand- “to glow, to shine.”

Etymology (PE): Šam’, loan from Ar.

The Hunting Dogs. A small → constellation in the northern hemisphere at approximate position: R.A. 7h, Dec. +40°. Abbreviation: CVn, genitive form: Canum Venaticorum.

Etymology (EN): L. Canes Venatic from canes, pl. of canis “dog” + venatici, pl. of venaticus “hunting.” The constellation was created by the Polish astronomer Johannes Hevelius in his sky chart of 1687.

Etymology (PE): Tâzi “greyhound, hunting dog,” originally “swift, fast,” from tâzidan, tâxtan “to run, to assault, to chase,” Av. tak- “to run,” Skt. talki “he rushes at,” O.S. techim “to run away,” Lith. teku “to run, flow.” Sagân-e Tâzi, from sagân pl. of sag “dog” → Canis Major + tâzi.

The Hunting Dogs. A small → constellation in the northern hemisphere at approximate position: R.A. 7h, Dec. +40°. Abbreviation: CVn, genitive form: Canum Venaticorum.

Etymology (EN): L. Canes Venatic from canes, pl. of canis “dog” + venatici, pl. of venaticus “hunting.” The constellation was created by the Polish astronomer Johannes Hevelius in his sky chart of 1687.

Etymology (PE): Tâzi “greyhound, hunting dog,” originally “swift, fast,” from tâzidan, tâxtan “to run, to assault, to chase,” Av. tak- “to run,” Skt. talki “he rushes at,” O.S. techim “to run away,” Lith. teku “to run, flow.” Sagân-e Tâzi, from sagân pl. of sag “dog” → Canis Major + tâzi.

The Greater Dog. A → constellation in the southern hemisphere which contains → Sirius, the brightest star of the whole sky. Approximate position: R.A. 7 h, Dec. -20°; abbreviation CMa; genitive form Canis Majoris.

Etymology (EN): L. Canis Major, from canis “dog” (cf. Gk. kuon, Skt. svâ-, Av. spâ-, Pers. sag; PIE *kwon-) + Maior “larger,” from L. major, irregular comp. of magnus “large, great” (cf. Gk. megas, Av. maz-, masan-, mazant- “great, important,” Skt. mah-, mahant-, Mod.Pers. meh; PIE *meg- “great”).
Canis Major is usually seen as one of the two hunting dogs of the hunter Orion. The other dog is Canis Minor, the Little Dog.

Etymology (PE): Sag-e Bozorg, from sag, see the above paragraph, + bozorg “large, great,” Mid.Pers. vuzurg, O.Pers. vazarka- “great,” Av. vazra- “club,” Skt. vajati, vaja- “strength,” vajra- “Indira’s thunderbolt,” L. vegere “to be lively,” PIE *weg- “to be strong, be lively.”

The Greater Dog. A → constellation in the southern hemisphere which contains → Sirius, the brightest star of the whole sky. Approximate position: R.A. 7 h, Dec. -20°; abbreviation CMa; genitive form Canis Majoris.

Etymology (EN): L. Canis Major, from canis “dog” (cf. Gk. kuon, Skt. svâ-, Av. spâ-, Pers. sag; PIE *kwon-) + Maior “larger,” from L. major, irregular comp. of magnus “large, great” (cf. Gk. megas, Av. maz-, masan-, mazant- “great, important,” Skt. mah-, mahant-, Mod.Pers. meh; PIE *meg- “great”).
Canis Major is usually seen as one of the two hunting dogs of the hunter Orion. The other dog is Canis Minor, the Little Dog.

Etymology (PE): Sag-e Bozorg, from sag, see the above paragraph, + bozorg “large, great,” Mid.Pers. vuzurg, O.Pers. vazarka- “great,” Av. vazra- “club,” Skt. vajati, vaja- “strength,” vajra- “Indira’s thunderbolt,” L. vegere “to be lively,” PIE *weg- “to be strong, be lively.”

The Lesser Dog. A small → constellation in the equatorial region of the northern sky at approximately R.A. 7h 30m, Dec. +5°. It hosts the bright star → Procyon. Abbreviation CMi, genitive form Canis Minoris.

Etymology (EN): Canis Minor, from canis “dog” → Canis Major; L. minor “lesser, smaller,” from PIE base *min- “small” (cf. Gk. meion “less, lesser,” Skt. mi-, minati “to diminish.”

Etymology (PE): Sag “dog,” → Canis Major; kucak “small,” from Mid.Pers. kok, kotak, kotah “small, short; child.”

The Lesser Dog. A small → constellation in the equatorial region of the northern sky at approximately R.A. 7h 30m, Dec. +5°. It hosts the bright star → Procyon. Abbreviation CMi, genitive form Canis Minoris.

Etymology (EN): Canis Minor, from canis “dog” → Canis Major; L. minor “lesser, smaller,” from PIE base *min- “small” (cf. Gk. meion “less, lesser,” Skt. mi-, minati “to diminish.”

Etymology (PE): Sag “dog,” → Canis Major; kucak “small,” from Mid.Pers. kok, kotak, kotah “small, short; child.”

Canon of Eclipses. The most famous catalogue of solar and lunar eclipses. Published in 1887 by Theodor von Oppolzer, the catalogue contains the elements of all solar and lunar eclipses between 1208 BC and 2161 AD. It has been superseded by the calculations of F. Espenak and J. Meeus, Five Millennium Canon of Solar Eclipses: -1999 to +3000 (NASA/TP-2006-214141) and Five Millennium Canon of Lunar Eclipses: -1999 to +3000 (NASA/TP-2009-214172).

Etymology (EN): Canon, from L. canon, from Gk. kanon “a straight rod, a measuring rod, rule;” Ger. Finsternisse, plural from finsternis “eclipse; darkness,” from finster “dark,” M.H.G. vinster, O.H.G. finstar “dark” + -nis suffix forming abstract nouns, → -ness.

Etymology (PE): Fehrest “index, catalogue, canon,” → index; gerefthâ plural of gereft, → eclipse.

Canon of Eclipses. The most famous catalogue of solar and lunar eclipses. Published in 1887 by Theodor von Oppolzer, the catalogue contains the elements of all solar and lunar eclipses between 1208 BC and 2161 AD. It has been superseded by the calculations of F. Espenak and J. Meeus, Five Millennium Canon of Solar Eclipses: -1999 to +3000 (NASA/TP-2006-214141) and Five Millennium Canon of Lunar Eclipses: -1999 to +3000 (NASA/TP-2009-214172).

Etymology (EN): Canon, from L. canon, from Gk. kanon “a straight rod, a measuring rod, rule;” Ger. Finsternisse, plural from finsternis “eclipse; darkness,” from finster “dark,” M.H.G. vinster, O.H.G. finstar “dark” + -nis suffix forming abstract nouns, → -ness.

Etymology (PE): Fehrest “index, catalogue, canon,” → index; gerefthâ plural of gereft, → eclipse.

1. General: Pertaining to, established by, or conforming to a canon, i.e. a law or a general rule (especially in ecclesiastical matters).
   
2. Math.: Relating to the simplest or standard form of a general function, equation, rule, etc.

Etymology (EN): M.M. canonicalis, from canonic(us), from L. canon, from Gk. kanon “a straight rod, a measuring rod, rule " + alis, → -al.

Etymology (PE): Hanjârvâr, from hanjâr “a mason’s rule, any string or instrument used by builders in laying stones straight; rule, law, way, custom; a norm” + -vâr suffix meaning “having, endowed with; like, in the manner of.”

1. General: Pertaining to, established by, or conforming to a canon, i.e. a law or a general rule (especially in ecclesiastical matters).
   
2. Math.: Relating to the simplest or standard form of a general function, equation, rule, etc.

Etymology (EN): M.M. canonicalis, from canonic(us), from L. canon, from Gk. kanon “a straight rod, a measuring rod, rule " + alis, → -al.

Etymology (PE): Hanjârvâr, from hanjâr “a mason’s rule, any string or instrument used by builders in laying stones straight; rule, law, way, custom; a norm” + -vâr suffix meaning “having, endowed with; like, in the manner of.”

A periodic change in one of the components of the orbit of a celestial object.

See also: → canonical; → change.

A periodic change in one of the components of the orbit of a celestial object.

See also: → canonical; → change.

Any set of generalized coordinates of a system together with their → conjugate momenta.

See also: → canonical; → coordinates.

Any set of generalized coordinates of a system together with their → conjugate momenta.

See also: → canonical; → coordinates.

The highest correlation between linear functions of two data sets
when specific restrictions are imposed upon them.

See also: → canonical; → correlation.

The highest correlation between linear functions of two data sets
when specific restrictions are imposed upon them.

See also: → canonical; → correlation.

The most general form of an equation.

See also: → canonical; → equation.

The most general form of an equation.

See also: → canonical; → equation.

The simplest expression of an equation, statement, or rule.

→ canonical; → form.

The simplest expression of an equation, statement, or rule.

→ canonical; → form.

A two-component stellar → initial mass function with → slopes of 1.3 and 2.3 for massive and low mass stars, respectively. Also called universal IMF.

See also: → canonical; → IMF.

A two-component stellar → initial mass function with → slopes of 1.3 and 2.3 for massive and low mass stars, respectively. Also called universal IMF.

See also: → canonical; → IMF.

A model for the formation of the Moon according to which the → Moon results from a giant impact. A Mars-sized body (often referred to as → Theia) obliquely collided with the proto-Earth at the mutual escapee velocity. This specific giant impact is often used to represent all giant impacts. A recent advanced version of the canonical model is called → giant impact hypothesis.

See also: → canonical; → model.

A model for the formation of the Moon according to which the → Moon results from a giant impact. A Mars-sized body (often referred to as → Theia) obliquely collided with the proto-Earth at the mutual escapee velocity. This specific giant impact is often used to represent all giant impacts. A recent advanced version of the canonical model is called → giant impact hypothesis.

See also: → canonical; → model.

Same as → conjugate momentum.

See also: → canonical; → momentum.

Same as → conjugate momentum.

See also: → canonical; → momentum.

A physical upper mass limit near 150 Msun assumed for the stellar → initial mass function (Kroupa et al. 2012, arXiv:1112.3340).

See also: → canonical; → upper; → limit.

A physical upper mass limit near 150 Msun assumed for the stellar → initial mass function (Kroupa et al. 2012, arXiv:1112.3340).

See also: → canonical; → upper; → limit.

A generalized coordinate and its → conjugate momentum.

Etymology (EN): Canonically, adverb from → canonical; → conjugate; → variable.

A generalized coordinate and its → conjugate momentum.

Etymology (EN): Canonically, adverb from → canonical; → conjugate; → variable.

The brightest star in the → constellation  → Carina and the second brightest star in the sky with a → visual magnitude -0.72. Also called α Carinae and HD45348. Canopus is not visible from latitudes above 37 degrees north. It is an evolved star, a → supergiant of type F0 II (Smiljanic et al., 2006, A&A 449, 655). Canopus lies 310 → light-years (96 → parsecs) from the Solar System; this is based on its → Hipparcos  → parallax measurement of 10.43 mas (5% accuracy). From this distance a → luminosity 13,300 times that the → solar luminosity is derived, and a radius of 73 times solar, in agreement with the → angular size (6.95 ± 0.15 mas) measured using → interferometry (Cruzalèbes et al., 2013, arXiv:1306.3288). These observations also yield an → effective temperature of about 7400 K. The star’s mass is estimated to be about 8 Msun. Canopus possesses an extremely hot magnetically heated → corona. Canopus’s corona is some 10 times hotter than the → solar corona and produces both observable → X-rays and → radio emission. According to calculations by J. Tomkin (1998, Sky & Telescope 95, 59), using → Hipparcos data, Canopus has, in the past, been the brightest star during three periods: from 3,700,000 to 1,370,000 years ago, from 950,000 to 420,000 years ago, and from 160,000 to 90,000 years ago. It will, once more, become the brightest star in 480,000 years and will remain such for 510,000 years.

Etymology (EN): Canopus, from Gk. kanobos, perhaps from Coptic language Kahi Nub “golden earth.”

Etymology (PE): Soheyl, from Ar. Suhail.
Agast, either a loan from Skt., or a possible, vanished Av. counterpart of Skt. Agasti, Agastya. The Skt. word derives from aga- “mountain,” and asti- “thrower.” In Vedic literature, Canopus is associated with the sage Agastya, one of the ancient rishis. The star is said to be the “cleanser of waters” because of turbid waters becoming clean at its rising.
Parak, of unknown etymology.

The brightest star in the → constellation  → Carina and the second brightest star in the sky with a → visual magnitude -0.72. Also called α Carinae and HD45348. Canopus is not visible from latitudes above 37 degrees north. It is an evolved star, a → supergiant of type F0 II (Smiljanic et al., 2006, A&A 449, 655). Canopus lies 310 → light-years (96 → parsecs) from the Solar System; this is based on its → Hipparcos  → parallax measurement of 10.43 mas (5% accuracy). From this distance a → luminosity 13,300 times that the → solar luminosity is derived, and a radius of 73 times solar, in agreement with the → angular size (6.95 ± 0.15 mas) measured using → interferometry (Cruzalèbes et al., 2013, arXiv:1306.3288). These observations also yield an → effective temperature of about 7400 K. The star’s mass is estimated to be about 8 Msun. Canopus possesses an extremely hot magnetically heated → corona. Canopus’s corona is some 10 times hotter than the → solar corona and produces both observable → X-rays and → radio emission. According to calculations by J. Tomkin (1998, Sky & Telescope 95, 59), using → Hipparcos data, Canopus has, in the past, been the brightest star during three periods: from 3,700,000 to 1,370,000 years ago, from 950,000 to 420,000 years ago, and from 160,000 to 90,000 years ago. It will, once more, become the brightest star in 480,000 years and will remain such for 510,000 years.

Etymology (EN): Canopus, from Gk. kanobos, perhaps from Coptic language Kahi Nub “golden earth.”

Etymology (PE): Soheyl, from Ar. Suhail.
Agast, either a loan from Skt., or a possible, vanished Av. counterpart of Skt. Agasti, Agastya. The Skt. word derives from aga- “mountain,” and asti- “thrower.” In Vedic literature, Canopus is associated with the sage Agastya, one of the ancient rishis. The star is said to be the “cleanser of waters” because of turbid waters becoming clean at its rising.
Parak, of unknown etymology.

1. A covering for the head.
   

2. The top part of something (such as a hill or mountain). → polar cap.
   

3. A removable cover or lid.

Etymology (EN): M.E. cappe; O.E. cæppe “hood, head-covering,” from L.L. cappa “a cape, hooded cloak,” possibly shortened from capitulare “headdress,” from L. caput “head;” cf. Pers. Lori kapu “head,” kapulek “skull, middle of the head;” Kurd. Kurmanji qaf “head;” Pashto kaparay “skull;” Farâhâni kapâl “a blow on the head.”

Etymology (PE): Kolâhak, diminutive of kolâh “cap;” maybe related to PIE base *kel- “conceal;” cf. L. celare “to hide, conceal,” occulere “to dissimulate;” Gk. kalyptein “to cover,” kalia “hut, nest;” Skt. cala “hut, house;” Goth. hilms “helmet,” huljan “cover over,” hulistr “covering;” E. hull “seed covering,”
from O.E. hulu, from O.H.G. hulla, hulsa; O.E. hol “cave;”

1. A covering for the head.
   

2. The top part of something (such as a hill or mountain). → polar cap.
   

3. A removable cover or lid.

Etymology (EN): M.E. cappe; O.E. cæppe “hood, head-covering,” from L.L. cappa “a cape, hooded cloak,” possibly shortened from capitulare “headdress,” from L. caput “head;” cf. Pers. Lori kapu “head,” kapulek “skull, middle of the head;” Kurd. Kurmanji qaf “head;” Pashto kaparay “skull;” Farâhâni kapâl “a blow on the head.”

Etymology (PE): Kolâhak, diminutive of kolâh “cap;” maybe related to PIE base *kel- “conceal;” cf. L. celare “to hide, conceal,” occulere “to dissimulate;” Gk. kalyptein “to cover,” kalia “hut, nest;” Skt. cala “hut, house;” Goth. hilms “helmet,” huljan “cover over,” hulistr “covering;” E. hull “seed covering,”
from O.E. hulu, from O.H.G. hulla, hulsa; O.E. hol “cave;”

The ratio of the charge Q on either conductor of a → capacitor to the → potential difference, or → voltage V between the conductors. It is given by C = Q/V. Capacitance can also be described by the relation:

C = ε₀A/d, where

ε₀ is the → permeability of free space, A is the area of one capacitor plate, and d is the distance between the capacitor plates. Capacitance is measured in → farads or, for convenience, in microfarads.

Etymology (EN): From capacit(y), → capacity + → -ance, a suffix used to form nouns either from adjectives in -ant or from verbs.

Etymology (PE): Gonjâyi, from gonjâ “able to hold,” from gonjidan→ capacity + -yi noun suffix.

The ratio of the charge Q on either conductor of a → capacitor to the → potential difference, or → voltage V between the conductors. It is given by C = Q/V. Capacitance can also be described by the relation:

C = ε₀A/d, where

ε₀ is the → permeability of free space, A is the area of one capacitor plate, and d is the distance between the capacitor plates. Capacitance is measured in → farads or, for convenience, in microfarads.

Etymology (EN): From capacit(y), → capacity + → -ance, a suffix used to form nouns either from adjectives in -ant or from verbs.

Etymology (PE): Gonjâyi, from gonjâ “able to hold,” from gonjidan→ capacity + -yi noun suffix.

A device for storing electric charge. The simplest sort of capacitors consists of two parallel, conductive plates having equal amounts of opposite charges and separated by a → dielectric material. When a capacitor is fully charged there is a → potential difference
between its plates. The larger the area of the plates and/or the smaller the separation between them the greater will be the charge that the capacitor can hold and the greater will be its → capacitance. The actual charge Q on the plates of a capacitor is given by: Q = C . V, where C is the capacitance and V the → voltage.

Etymology (EN): From capacit-, from → capacity + → -or.

Etymology (PE): From gonjân transitive stem of gonjidan “to be contained; to hold exactly; to be filled,” → capacity, + -gar, → -or.

A device for storing electric charge. The simplest sort of capacitors consists of two parallel, conductive plates having equal amounts of opposite charges and separated by a → dielectric material. When a capacitor is fully charged there is a → potential difference
between its plates. The larger the area of the plates and/or the smaller the separation between them the greater will be the charge that the capacitor can hold and the greater will be its → capacitance. The actual charge Q on the plates of a capacitor is given by: Q = C . V, where C is the capacitance and V the → voltage.

Etymology (EN): From capacit-, from → capacity + → -or.

Etymology (PE): From gonjân transitive stem of gonjidan “to be contained; to hold exactly; to be filled,” → capacity, + -gar, → -or.

The ability to receive or contain.
Electricity: → capacitance.

Etymology (EN): From M.Fr. capacité, from L. capacitatem, from capax “able to hold much,” from capere “to take, grasp.”

Etymology (PE): Gonjâyeš “capacity, holding, containing,” from gonjdan “to be contained; to hold exactly; to be filled;” Mid.Pers. winj- “to be contained;” Proto-Iranian *uiac-/*uic-; cf. Skt. vyac- “to contain, encompass,” vyás- “extent, content, extension;” L. uincire “to bind.”

The ability to receive or contain.
Electricity: → capacitance.

Etymology (EN): From M.Fr. capacité, from L. capacitatem, from capax “able to hold much,” from capere “to take, grasp.”

Etymology (PE): Gonjâyeš “capacity, holding, containing,” from gonjdan “to be contained; to hold exactly; to be filled;” Mid.Pers. winj- “to be contained;” Proto-Iranian *uiac-/*uic-; cf. Skt. vyac- “to contain, encompass,” vyás- “extent, content, extension;” L. uincire “to bind.”

The sixth brightest star in the sky, Capella lies in the Northern Hemisphere → constellation  → Auriga. Also known as HD 34029 = HR 1708 = HIP 24608.

Capella lies about 42 → light-years away (13.159 ± 0.015 → parsecs).

Its → apparent visual magnitude is V = 0.07. A → spectroscopic binary, it consists of a pair of G8 III and G0 III → giants with an → orbital period of 104 days.

The more evolved former/→ primary star has a slightly larger mass and luminosity (2.6 Msun and 79 Lsun) than that of the latter/→ secondary star (2.5 Msun and 73 Lsun). The primary is a typical late G giant presumably in the He-burning stage (→ red clump), which is lithium deficient and a slow rotator as other normal giants. In contrast, the secondary is a fast rotator (projected rotational velocity is v_e sin i ~ 35 km s-1) with high stellar activity (characterized by conspicuous chromospheric emission lines in UV) and shows a remarkably strong Li line, which indicates that the initial Li content is almost retained without being diluted (the surface Li composition for the secondary is ~100 times higher than that for the primary). That is, the secondary star belongs to the unusual group of Li-rich giants (see, e.g., Takeda et al., 2018, ApJ 862, 57 and Torres et al., 2015, ApJ 807, 26).

Etymology (EN): From L. capella “little she-goat,” diminutive of caper “goat.”

Etymology (PE): Bozbân “goat keeper” (Biruni, A.D. 973-1048, in his Tafhim), from boz, → goat, + -bân prefix denoting “keeper.”
Ayyuq, loan from Ar.

The sixth brightest star in the sky, Capella lies in the Northern Hemisphere → constellation  → Auriga. Also known as HD 34029 = HR 1708 = HIP 24608.

Capella lies about 42 → light-years away (13.159 ± 0.015 → parsecs).

Its → apparent visual magnitude is V = 0.07. A → spectroscopic binary, it consists of a pair of G8 III and G0 III → giants with an → orbital period of 104 days.

The more evolved former/→ primary star has a slightly larger mass and luminosity (2.6 Msun and 79 Lsun) than that of the latter/→ secondary star (2.5 Msun and 73 Lsun). The primary is a typical late G giant presumably in the He-burning stage (→ red clump), which is lithium deficient and a slow rotator as other normal giants. In contrast, the secondary is a fast rotator (projected rotational velocity is v_e sin i ~ 35 km s-1) with high stellar activity (characterized by conspicuous chromospheric emission lines in UV) and shows a remarkably strong Li line, which indicates that the initial Li content is almost retained without being diluted (the surface Li composition for the secondary is ~100 times higher than that for the primary). That is, the secondary star belongs to the unusual group of Li-rich giants (see, e.g., Takeda et al., 2018, ApJ 862, 57 and Torres et al., 2015, ApJ 807, 26).

Etymology (EN): From L. capella “little she-goat,” diminutive of caper “goat.”

Etymology (PE): Bozbân “goat keeper” (Biruni, A.D. 973-1048, in his Tafhim), from boz, → goat, + -bân prefix denoting “keeper.”
Ayyuq, loan from Ar.

Same as → capillary action.

See also: → capillary; → -ity.

Same as → capillary action.

See also: → capillary; → -ity.

1. Resembling a strand of hair; hairlike.
   

2. Pertaining to or occurring in or as if in a tube of fine bore.
   

3. Physics: Pertaining to → capillarity.
   

4. Anatomy: One of the minute blood vessels between the terminations of the arteries and the beginnings of the veins (Dictionary.com).

Etymology (EN): From L. capillaris “pertaining to hair,” from capillus “hair.”

Etymology (PE): Muyin, muyiné, from mu(y), → hair.

1. Resembling a strand of hair; hairlike.
   

2. Pertaining to or occurring in or as if in a tube of fine bore.
   

3. Physics: Pertaining to → capillarity.
   

4. Anatomy: One of the minute blood vessels between the terminations of the arteries and the beginnings of the veins (Dictionary.com).

Etymology (EN): From L. capillaris “pertaining to hair,” from capillus “hair.”

Etymology (PE): Muyin, muyiné, from mu(y), → hair.

The ability of a → liquid to → flow in a → narrow space, such as a thin → tube, without the assistance of, and in opposition to, external forces like → gravity. Also called → capillarity. It
occurs because of intermolecular → attractive forces between the liquid and solid surrounding surfaces. If the diameter of the tube is sufficiently small, then the combination of → surface tension (which is caused by → cohesion within the liquid) and → adhesion (between the liquid and the → container) acts to lift the liquid. The capillarity of the liquid is high when adhesion is greater than cohesion. For example, water in a thin glass tube has strong → adhesive forces due to the hydrogen bonds that form between the water molecules and the oxygen atoms in the glass wall (made of → silica, SiO₂). In contrast, mercury is characterized by stronger cohesion, and hence its capillarity is much lower.

See also: → capillary; → action.

The ability of a → liquid to → flow in a → narrow space, such as a thin → tube, without the assistance of, and in opposition to, external forces like → gravity. Also called → capillarity. It
occurs because of intermolecular → attractive forces between the liquid and solid surrounding surfaces. If the diameter of the tube is sufficiently small, then the combination of → surface tension (which is caused by → cohesion within the liquid) and → adhesion (between the liquid and the → container) acts to lift the liquid. The capillarity of the liquid is high when adhesion is greater than cohesion. For example, water in a thin glass tube has strong → adhesive forces due to the hydrogen bonds that form between the water molecules and the oxygen atoms in the glass wall (made of → silica, SiO₂). In contrast, mercury is characterized by stronger cohesion, and hence its capillarity is much lower.

See also: → capillary; → action.

→ Tropic of Capricorn.

See also: → Capricornus.

→ Tropic of Capricorn.

See also: → Capricornus.

The Sea Goat. The smallest → constellation of the → Zodiac, lying in the Southern Hemisphere at approximately R.A. 21h, Dec. -20°.
Abbreviation Cap; genitive form Capricorni.

Etymology (EN): L. Capricornus “horned like a goat,” from caper “goat” + cornu “horn” (Gk. karnon, Skt. srnga-, Av. sru-, srvâ-, Mid.Pers. sruw, Mod.Pers. soru, P.Gmc. *khurnaz, Ger. Horn, E. horn, PIE *ker- “head, horn, top, summit”), a translation of Gk. Aigokheros, the name of the constellation.

Etymology (PE): Vahig, Mid.Pers. “goat,” the name of the Capricorn sign in Mid.Pers. texts, Mod.Pers. bahi, as mentioned by Biruni in his Athar al-Baqia written around A.D. 1000.

The Sea Goat. The smallest → constellation of the → Zodiac, lying in the Southern Hemisphere at approximately R.A. 21h, Dec. -20°.
Abbreviation Cap; genitive form Capricorni.

Etymology (EN): L. Capricornus “horned like a goat,” from caper “goat” + cornu “horn” (Gk. karnon, Skt. srnga-, Av. sru-, srvâ-, Mid.Pers. sruw, Mod.Pers. soru, P.Gmc. *khurnaz, Ger. Horn, E. horn, PIE *ker- “head, horn, top, summit”), a translation of Gk. Aigokheros, the name of the constellation.

Etymology (PE): Vahig, Mid.Pers. “goat,” the name of the Capricorn sign in Mid.Pers. texts, Mod.Pers. bahi, as mentioned by Biruni in his Athar al-Baqia written around A.D. 1000.

1. A title or explanation for a picture or illustration, especially in a magazine.
   

2. A heading or title, as of a chapter, article, or page (Dictionary.com).

Etymology (EN): M.E. capcio(u)n “taking, seizure,” from capcion “arrest, capture, imprisonment,” or directly from L. caption-, from capt(us) “taken,” → capture.

Etymology (PE): Kapéš “taking, capture,” verbal noun from kapidan
“to seize, take, capture,” related to qâpidan, qâp zadan “to rob, to seize,” Malâyeri qapâl “robbing, seizure, robbing,” probably related to L. capere, → capture.

1. A title or explanation for a picture or illustration, especially in a magazine.
   

2. A heading or title, as of a chapter, article, or page (Dictionary.com).

Etymology (EN): M.E. capcio(u)n “taking, seizure,” from capcion “arrest, capture, imprisonment,” or directly from L. caption-, from capt(us) “taken,” → capture.

Etymology (PE): Kapéš “taking, capture,” verbal noun from kapidan
“to seize, take, capture,” related to qâpidan, qâp zadan “to rob, to seize,” Malâyeri qapâl “robbing, seizure, robbing,” probably related to L. capere, → capture.

The process in which an atomic, nuclear, or astronomical system acquires an additional particle or body.

Etymology (EN): From M.Fr. capture “a taking,” from L. captura “a taking,” from captus p.p. of capere “to take, hold, seize;” PIE base *kap- “to grasp” (cf. Skt. kapati “measure equal to the capacity of the hollows of the two hands joined;” Gk. kaptein “to swallow;” O.Ir. cacht “servant-girl,” literally “captive;” Goth. haban “have, hold;” O.E. habban, E. have “to have, hold;” probably Mod.Pers. qâp-, qâpidan, kapidan “to seize, rob”).

Etymology (PE): Gir-oft, composite verb from gir + oft. Gir “take, seize, hold,” from gereftan, from O.Pers./Av. grab- “to take, seize,”
cf. Skt. grah-, grabh- “to seize, take,” graha- “seizing, holding, perceiving,” M.L.G. grabben “to grab,” from P.Gmc. *grab, E. grab “to take or grasp suddenly;” PIE *ghrebh- “to seize.” Oft, from oftâtan “to fall; to befal, happen,” Mid.Pers. opastan, Av. pat- " to fly, fall, rush," Skt. patati “he flies, falls,” L. petere “to fall, rush out,” Gk. piptein “to fall,” PIE base *pet- “to fly, to rush.” Gir-andâzi, from gir + andâzi, verbal noun from gir-andâxtan “to throw, cast; to do, make.”

The process in which an atomic, nuclear, or astronomical system acquires an additional particle or body.

Etymology (EN): From M.Fr. capture “a taking,” from L. captura “a taking,” from captus p.p. of capere “to take, hold, seize;” PIE base *kap- “to grasp” (cf. Skt. kapati “measure equal to the capacity of the hollows of the two hands joined;” Gk. kaptein “to swallow;” O.Ir. cacht “servant-girl,” literally “captive;” Goth. haban “have, hold;” O.E. habban, E. have “to have, hold;” probably Mod.Pers. qâp-, qâpidan, kapidan “to seize, rob”).

Etymology (PE): Gir-oft, composite verb from gir + oft. Gir “take, seize, hold,” from gereftan, from O.Pers./Av. grab- “to take, seize,”
cf. Skt. grah-, grabh- “to seize, take,” graha- “seizing, holding, perceiving,” M.L.G. grabben “to grab,” from P.Gmc. *grab, E. grab “to take or grasp suddenly;” PIE *ghrebh- “to seize.” Oft, from oftâtan “to fall; to befal, happen,” Mid.Pers. opastan, Av. pat- " to fly, fall, rush," Skt. patati “he flies, falls,” L. petere “to fall, rush out,” Gk. piptein “to fall,” PIE base *pet- “to fly, to rush.” Gir-andâzi, from gir + andâzi, verbal noun from gir-andâxtan “to throw, cast; to do, make.”

One of the first scientific hypotheses about the formation of the Moon, according to which the Moon formed elsewhere in the solar system and was pulled into a stable orbit by Earth’s gravity.

Observational facts do not confirm this hypothesis. For example, analysis of rocks from the Apollo landings confirm the Moon is made of similar material and rock as the Earth from about the same time and have almost identical oxygen isotopes in them.

Moreover, a captured moon, like Mars’ → Phobos and → Deimos do not have a spherical shape. See also → giant impact hypothesis, → fission theory, → co-formation theory.

See also: → capture; → theory.

One of the first scientific hypotheses about the formation of the Moon, according to which the Moon formed elsewhere in the solar system and was pulled into a stable orbit by Earth’s gravity.

Observational facts do not confirm this hypothesis. For example, analysis of rocks from the Apollo landings confirm the Moon is made of similar material and rock as the Earth from about the same time and have almost identical oxygen isotopes in them.

Moreover, a captured moon, like Mars’ → Phobos and → Deimos do not have a spherical shape. See also → giant impact hypothesis, → fission theory, → co-formation theory.

See also: → capture; → theory.

A combining form used in the names of → chemical compounds in which → carbon is present. Also, especially before a vowel, carb-.

See also: From → carbon.

A combining form used in the names of → chemical compounds in which → carbon is present. Also, especially before a vowel, carb-.

See also: From → carbon.

A molecular compound made from just three → chemical elements: → carbon, → hydrogen, and → oxygen. Carbohydrates have the general molecular formula C_xH_2yO_y, and thus were once thought to represent “hydrated carbon.” However, the arrangement of atoms in carbohydrates has little to do with → water molecules. Carbohydrates are a source of energy for the body. They include sugars, starches, cellulose and many other compounds found in living organisms. In their basic form, carbohydrates are simple sugars or monosaccharides.

See also: → carbo-; → hydrate.

A molecular compound made from just three → chemical elements: → carbon, → hydrogen, and → oxygen. Carbohydrates have the general molecular formula C_xH_2yO_y, and thus were once thought to represent “hydrated carbon.” However, the arrangement of atoms in carbohydrates has little to do with → water molecules. Carbohydrates are a source of energy for the body. They include sugars, starches, cellulose and many other compounds found in living organisms. In their basic form, carbohydrates are simple sugars or monosaccharides.

See also: → carbo-; → hydrate.

Nonmetallic chemical element; symbol C. → Atomic number 6; → atomic weight 12.011; → melting point about 3,550°C; → boiling point 4,827°C. The most abundant isotope of carbon is ¹²C. Carbon is one of the most important elements for life. The burning of carbon in the form of coal and oils has been essential in the development of industrial societies. It is the element that hardens → steel and the sole element in → diamonds. The carbon in nature is produced inside massive stars. → triple-alpha process; → Hoyle state.

See also: Carbon, from Fr. carbone, coined by Antoine Lavoisier (1743-1794) to distinguish it from charbon (Fr.) “charcoal,” from L. carbo
(genitive carbonis) “a coal, charcoal.”

Nonmetallic chemical element; symbol C. → Atomic number 6; → atomic weight 12.011; → melting point about 3,550°C; → boiling point 4,827°C. The most abundant isotope of carbon is ¹²C. Carbon is one of the most important elements for life. The burning of carbon in the form of coal and oils has been essential in the development of industrial societies. It is the element that hardens → steel and the sole element in → diamonds. The carbon in nature is produced inside massive stars. → triple-alpha process; → Hoyle state.

See also: Carbon, from Fr. carbone, coined by Antoine Lavoisier (1743-1794) to distinguish it from charbon (Fr.) “charcoal,” from L. carbo
(genitive carbonis) “a coal, charcoal.”

The stage in the evolution of a star after → helium burning when the core of the star consists mainly of carbon and oxygen. In stars of mass greater than about 8 solar masses, whose cores reach a temperature above 5 × 10⁸ K and density above 3 × 10⁹ kg m^-3, carbon burning can begin via reactions such as the following:
¹²C + ¹²C → ²⁰Ne + ⁴He
¹²C + ¹²C → ²³Na + p
¹²C + ¹²C → ²³Mg + n.
The time-scale for this phase of → nucleosynthesis is of order of five hundred years.

See also: → carbon; → burning.

The stage in the evolution of a star after → helium burning when the core of the star consists mainly of carbon and oxygen. In stars of mass greater than about 8 solar masses, whose cores reach a temperature above 5 × 10⁸ K and density above 3 × 10⁹ kg m^-3, carbon burning can begin via reactions such as the following:
¹²C + ¹²C → ²⁰Ne + ⁴He
¹²C + ¹²C → ²³Na + p
¹²C + ¹²C → ²³Mg + n.
The time-scale for this phase of → nucleosynthesis is of order of five hundred years.

See also: → carbon; → burning.

A problem raised in the past by observations suggesting that the amount of carbon necessary for standard → dust models was larger than what actually observed for the → interstellar medium (ISM) (Snow & Witt 1995). The problem was especially acute for the → 2175 A bump in the ultraviolet part of the → extinction curve. The so-called “crisis” was finally solved by, on the one hand, revising downward the → solar abundances, thought to represent the ISM abundances (Asplund et al. 2009, arXiv:0909.0948, and references therein), and, on the other hand, revising upward the ISM carbon abundances (Sofia et al., 2011, AJ 141, 22S).

See also: → carbon; → crisis.

A problem raised in the past by observations suggesting that the amount of carbon necessary for standard → dust models was larger than what actually observed for the → interstellar medium (ISM) (Snow & Witt 1995). The problem was especially acute for the → 2175 A bump in the ultraviolet part of the → extinction curve. The so-called “crisis” was finally solved by, on the one hand, revising downward the → solar abundances, thought to represent the ISM abundances (Asplund et al. 2009, arXiv:0909.0948, and references therein), and, on the other hand, revising upward the ISM carbon abundances (Sofia et al., 2011, AJ 141, 22S).

See also: → carbon; → crisis.

1. A complex series of processes through which all the carbon atoms on Earth is cycled through the air, ground, plants, animals, and fossil fuels. During the cycle, plants absorb → carbon dioxide (CO₂) from the atmosphere and through → photosynthesis incorporate the associated carbon atoms into sugars and other molecules necessary for growth. Plants return carbon atoms back to the atmosphere in the form of CO₂. However, much of the carbon absorbed remains “locked up” in the living organisms until decomposition or fire releases it back to the atmosphere.
   

2. For nuclear fusion in stars → CNO cycle.

See also: → carbon; → cycle.

1. A complex series of processes through which all the carbon atoms on Earth is cycled through the air, ground, plants, animals, and fossil fuels. During the cycle, plants absorb → carbon dioxide (CO₂) from the atmosphere and through → photosynthesis incorporate the associated carbon atoms into sugars and other molecules necessary for growth. Plants return carbon atoms back to the atmosphere in the form of CO₂. However, much of the carbon absorbed remains “locked up” in the living organisms until decomposition or fire releases it back to the atmosphere.
   

2. For nuclear fusion in stars → CNO cycle.

See also: → carbon; → cycle.

CO₂, also called carbonic acid gas. A colorless gas which occurs in the atmosphere playing an essential part in animal respiration and the growth of green plants. → photosynthesis, → carbon cycle. It is formed by the → oxidation of carbon and carbon compounds. Carbon dioxide is the most important → greenhouse gas produced by human activities, primarily through the combustion of fossil fuels. Its concentration in the Earth’s atmosphere has risen by more than 30% since the Industrial Revolution. CO₂ forms a solid at -78.5 °C at atmospheric pressure, and is used as a refrigerant in this form as a dry ice for the preservation of frozen foods. As carbon dioxide gas is heavier than air and does not support combustion, it is used in fire extinguishers.
CO₂ is present in the → interstellar medium and is one of the main → molecules in → comets.

See also: → carbon; → dioxide.

CO₂, also called carbonic acid gas. A colorless gas which occurs in the atmosphere playing an essential part in animal respiration and the growth of green plants. → photosynthesis, → carbon cycle. It is formed by the → oxidation of carbon and carbon compounds. Carbon dioxide is the most important → greenhouse gas produced by human activities, primarily through the combustion of fossil fuels. Its concentration in the Earth’s atmosphere has risen by more than 30% since the Industrial Revolution. CO₂ forms a solid at -78.5 °C at atmospheric pressure, and is used as a refrigerant in this form as a dry ice for the preservation of frozen foods. As carbon dioxide gas is heavier than air and does not support combustion, it is used in fire extinguishers.
CO₂ is present in the → interstellar medium and is one of the main → molecules in → comets.

See also: → carbon; → dioxide.

A colorless, odorless, very poisonous gas which burns in air with a bright blue flame to form → carbon dioxide. CO gives rise to a violent explosion when ignited in air in certain proportions. It occurs in coal gas and in the exhaust fumes of motor engines. Melting point -207 °C; boiling point -191.1 °C.

Carbon monoxide is the most important → molecule found in the → interstellar medium, and is produced through several chemical reactions, → CO formation. It was discovered in 1970 by R. Wilson and A. Penzias of Bell Laboratories, using the 11-m telescope of the National Radio Astronomy Observatory (NRAO) in the direction of the → Orion nebula. Because the CO line is so intense and widely distributed in space, this molecule is a most useful tool for tracing the ISM. In addition, measurement of its rare isotopes have shown that the main line ¹²C¹⁶O (wavelength 2.6 mm, 115 GHz) is
→ optically thick, that is the → column density of the molecule is so high that the material becomes opaque at the transition frequency. Moreover, the upper-energy levels of the CO molecule are easily excited by collision with → molecular hydrogen. The combination of high → optical depth and the ease of → excitation imply that CO emission brightness will accurately reflect the local gas temperature. CO is also one of the principal molecules detected in → comet nuclei.

See also: → carbon; → mono-; → oxide.

A colorless, odorless, very poisonous gas which burns in air with a bright blue flame to form → carbon dioxide. CO gives rise to a violent explosion when ignited in air in certain proportions. It occurs in coal gas and in the exhaust fumes of motor engines. Melting point -207 °C; boiling point -191.1 °C.

Carbon monoxide is the most important → molecule found in the → interstellar medium, and is produced through several chemical reactions, → CO formation. It was discovered in 1970 by R. Wilson and A. Penzias of Bell Laboratories, using the 11-m telescope of the National Radio Astronomy Observatory (NRAO) in the direction of the → Orion nebula. Because the CO line is so intense and widely distributed in space, this molecule is a most useful tool for tracing the ISM. In addition, measurement of its rare isotopes have shown that the main line ¹²C¹⁶O (wavelength 2.6 mm, 115 GHz) is
→ optically thick, that is the → column density of the molecule is so high that the material becomes opaque at the transition frequency. Moreover, the upper-energy levels of the CO molecule are easily excited by collision with → molecular hydrogen. The combination of high → optical depth and the ease of → excitation imply that CO emission brightness will accurately reflect the local gas temperature. CO is also one of the principal molecules detected in → comet nuclei.

See also: → carbon; → mono-; → oxide.

A class of → red giant stars whose spectra show strong → molecular bands of → carbon compounds.

See also: → carbon; → star.

A class of → red giant stars whose spectra show strong → molecular bands of → carbon compounds.

See also: → carbon; → star.

A radioactive isotope of carbon, whose nucleus contains 6 protons and 8 neutrons;
also called → radiocarbon. ¹⁴C is naturally produced in the atmosphere when a neutron created by a cosmic ray hits the nucleus of an atom of nitrogen-14. The nucleus absorbs the neutron and ejects a proton, thereby transforming itself into ¹⁴C. It decays back to nitrogen, with a half-life is 5730 years, after emitting an electron (¹⁴₆C → ¹⁴₇N + e^- + ν_e). See also → radiocarbon dating.

See also: → carbon; → four + -teen, an inflected form of the root of → ten.

A radioactive isotope of carbon, whose nucleus contains 6 protons and 8 neutrons;
also called → radiocarbon. ¹⁴C is naturally produced in the atmosphere when a neutron created by a cosmic ray hits the nucleus of an atom of nitrogen-14. The nucleus absorbs the neutron and ejects a proton, thereby transforming itself into ¹⁴C. It decays back to nitrogen, with a half-life is 5730 years, after emitting an electron (¹⁴₆C → ¹⁴₇N + e^- + ν_e). See also → radiocarbon dating.

See also: → carbon; → four + -teen, an inflected form of the root of → ten.

A star that presents very low → iron  → abundances [Fe/H] < -4 but an → anomalous richness in carbon. CEMP stars have been defined as a subset of → metal-poor stars that exhibit elevated [C/Fe] ≥ +1.0. It has been recognized that ~15-20% of stars with [Fe/H] < -2.0 are carbon enhanced. This fraction rises to 30% for [Fe/H] < -3.0, to 40% for [Fe/H] < -3.5, and ~75% for [Fe/H] < -4.0. This increasing trend of CEMP-star frequency with declining [Fe/H] is confirmed by the observation of many thousands of CEMP stars (Daniela Carollo + ApJ 2014, 788, 180). See also → extremely metal-poor star (EMPS)

See also: → carbon; → enhance; → metal; → metal; → poor; → star.

A star that presents very low → iron  → abundances [Fe/H] < -4 but an → anomalous richness in carbon. CEMP stars have been defined as a subset of → metal-poor stars that exhibit elevated [C/Fe] ≥ +1.0. It has been recognized that ~15-20% of stars with [Fe/H] < -2.0 are carbon enhanced. This fraction rises to 30% for [Fe/H] < -3.0, to 40% for [Fe/H] < -3.5, and ~75% for [Fe/H] < -4.0. This increasing trend of CEMP-star frequency with declining [Fe/H] is confirmed by the observation of many thousands of CEMP stars (Daniela Carollo + ApJ 2014, 788, 180). See also → extremely metal-poor star (EMPS)

See also: → carbon; → enhance; → metal; → metal; → poor; → star.

Containing or composed of carbon.

Etymology (EN): From → carbon + -aceous, from L. -aceus “-ous.”

Etymology (PE): Karboni, adj. from karbon, → carbon; karbondâr “having carbon,” with -dâr “having, possessor,” from dâštan “to have, to possess;” O.Pers./Av. root dar- “to hold, keep back, maintain, keep in mind;” cf. Skt. dhr-, dharma- “law;” Gk. thronos “elevated seat, throne;” L. firmus “firm, stable;” Lith. daryti “to make;” PIE base *dher- “to hold, support.”

Containing or composed of carbon.

Etymology (EN): From → carbon + -aceous, from L. -aceus “-ous.”

Etymology (PE): Karboni, adj. from karbon, → carbon; karbondâr “having carbon,” with -dâr “having, possessor,” from dâštan “to have, to possess;” O.Pers./Av. root dar- “to hold, keep back, maintain, keep in mind;” cf. Skt. dhr-, dharma- “law;” Gk. thronos “elevated seat, throne;” L. firmus “firm, stable;” Lith. daryti “to make;” PIE base *dher- “to hold, support.”

A rare type of → stony meteorite having a higher → carbon content than other classes of meteorite. They represent only ~5% of the known meteorites. Their bulk composition is mainly → silicates, → oxides and sulfides, whilst the minerals → olivine and serpentine are characteristic. The six classes of carbonaceous chondrites are: → CI chondrites, CM chondrites, CV chondrites, CO chondrites, CK chondrites, CR chondrites, CH chondrites, and CB chondrites.

See also: → carbonaceous; → chondrite.

A rare type of → stony meteorite having a higher → carbon content than other classes of meteorite. They represent only ~5% of the known meteorites. Their bulk composition is mainly → silicates, → oxides and sulfides, whilst the minerals → olivine and serpentine are characteristic. The six classes of carbonaceous chondrites are: → CI chondrites, CM chondrites, CV chondrites, CO chondrites, CK chondrites, CR chondrites, CH chondrites, and CB chondrites.

See also: → carbonaceous; → chondrite.

The radical -C=O, which occurs in several compounds, such as → aldehydes and ketones.

See also: From → carbon + -yl a suffix used in the names of some radicals; → group.

The radical -C=O, which occurs in several compounds, such as → aldehydes and ketones.

See also: From → carbon + -yl a suffix used in the names of some radicals; → group.

Chem.: The -COOH group, regarded as the essential and characteristic constituent of organic acids.

See also: From carb-, variant of carbo- before a vowel, from → carbon, + ox, from → oxygen,

• -yl a suffix used in the names of radicals.

Chem.: The -COOH group, regarded as the essential and characteristic constituent of organic acids.

See also: From carb-, variant of carbo- before a vowel, from → carbon, + ox, from → oxygen,

• -yl a suffix used in the names of radicals.

1. Fundamentally → important; → principal.
   

2. → cardinal number.

Etymology (EN): M.E., from L.L. cardinalis “principal, pivotal,” lit. “serving as a hinge,” from cardo, cardin- “door hinge.”

Etymology (PE): Agrâ, from Av. aγra-, aγrya- “the highest, the first, foremost” cf. Skt. agra- “foremost, first, prominent,” PIE *agro- “top, first, beginning.”

1. Fundamentally → important; → principal.
   

2. → cardinal number.

Etymology (EN): M.E., from L.L. cardinalis “principal, pivotal,” lit. “serving as a hinge,” from cardo, cardin- “door hinge.”

Etymology (PE): Agrâ, from Av. aγra-, aγrya- “the highest, the first, foremost” cf. Skt. agra- “foremost, first, prominent,” PIE *agro- “top, first, beginning.”

Any of the four principal directions or points of the compass, → north, → east, → south, and → west. See also: → cardinal point.

See also: → cardinal; → direction.

Any of the four principal directions or points of the compass, → north, → east, → south, and → west. See also: → cardinal point.

See also: → cardinal; → direction.

An ordinary number such as 0, 1, 2, or 3, as opposed to an → ordinal number such as 1st, 2nd, or 3rd. Cardinal numbers can be → zero or → positive
and are used for counting the things that are assumed to be not divisible.

See also: → cardinal; → number.

An ordinary number such as 0, 1, 2, or 3, as opposed to an → ordinal number such as 1st, 2nd, or 3rd. Cardinal numbers can be → zero or → positive
and are used for counting the things that are assumed to be not divisible.

See also: → cardinal; → number.

One of the four points where the → meridian and the → prime vertical intersect the → horizon. See also: → cardinal direction.

See also: → cardinal; → point.

One of the four points where the → meridian and the → prime vertical intersect the → horizon. See also: → cardinal direction.

See also: → cardinal; → point.

Math.: The → cardinal number indicating the → number of → elements in a → set. For example, the set A = {a, b, c, d} contains 4 elements, and therefore it has a cardinality of 4 (denoted |A| = 4).

See also: → cardinal; → -ity.

Math.: The → cardinal number indicating the → number of → elements in a → set. For example, the set A = {a, b, c, d} contains 4 elements, and therefore it has a cardinality of 4 (denoted |A| = 4).

See also: → cardinal; → -ity.

1a) A state of mind in which one is troubled; worry, anxiety, or concern;
a cause or object of worry, anxiety, concern, etc.

1b) Serious attention; solicitude; heed; caution.

2a) To be concerned or solicitous; have thought or regard.

2b) To be concerned or have a special preference (Dictionary.com).

Etymology (EN): M.E., from O.E. caru, cearu “sorrow, anxiety, grief,” cognate with Gothic kara, O.H.G. chara lament; M.En. caren, O.E. cearian, carian “be anxious, grieve.”

Etymology (PE): Timâr “care, attendance on the sick; custody; sorrow;” Mid.Pers. têmâr “care; grief”

1a) A state of mind in which one is troubled; worry, anxiety, or concern;
a cause or object of worry, anxiety, concern, etc.

1b) Serious attention; solicitude; heed; caution.

2a) To be concerned or solicitous; have thought or regard.

2b) To be concerned or have a special preference (Dictionary.com).

Etymology (EN): M.E., from O.E. caru, cearu “sorrow, anxiety, grief,” cognate with Gothic kara, O.H.G. chara lament; M.En. caren, O.E. cearian, carian “be anxious, grieve.”

Etymology (PE): Timâr “care, attendance on the sick; custody; sorrow;” Mid.Pers. têmâr “care; grief”

1. Cautious in one’s actions.
   

2. Taking pains in one’s work; exact; thorough.
   

3. (of things) Done or performed with accuracy or caution (Dictionary.com).

See also: → care; + -ful, a suffix meaning “characterized by; full of; able to;” → full.

1. Cautious in one’s actions.
   

2. Taking pains in one’s work; exact; thorough.
   

3. (of things) Done or performed with accuracy or caution (Dictionary.com).

See also: → care; + -ful, a suffix meaning “characterized by; full of; able to;” → full.

The Keel. A major → constellation in the southern sky, home to → Canopus (α Carinae), the second brightest star after → Sirius. Approximate position: RA 9h, Dec. -60° The constellation resulted from the division of a very large constellation representing → Argo Navis, the mythological Jason’s ship. The partition into the
constellations → Carina, → Puppis, → Vela, and → Pyxis appeared first on a sky map by Nicholas Louis de Lacaille (1763). Carina represents the bottom of the Ship Argo. Abbreviation:
Car; genitive form: Carinae.

Etymology (EN): L. carina “the keel of a ship, i.e. the principal structural member of a ship, running lengthwise along the center line from bow to stern, to which the frames are attached.”

Etymology (PE): Afzal “keel” in the jargon of the Caspian sea fishermen
of Gilan province. Šâh-taxté “main plank.”

The Keel. A major → constellation in the southern sky, home to → Canopus (α Carinae), the second brightest star after → Sirius. Approximate position: RA 9h, Dec. -60° The constellation resulted from the division of a very large constellation representing → Argo Navis, the mythological Jason’s ship. The partition into the
constellations → Carina, → Puppis, → Vela, and → Pyxis appeared first on a sky map by Nicholas Louis de Lacaille (1763). Carina represents the bottom of the Ship Argo. Abbreviation:
Car; genitive form: Carinae.

Etymology (EN): L. carina “the keel of a ship, i.e. the principal structural member of a ship, running lengthwise along the center line from bow to stern, to which the frames are attached.”

Etymology (PE): Afzal “keel” in the jargon of the Caspian sea fishermen
of Gilan province. Šâh-taxté “main plank.”

A → spiral arm in the Milky Way galaxy seen at its best in the → constellation → Carina, but also crossing the constellations → Vela,
→ Crux, and → Centaurus. It may be a continuation of the → Sagittarius arm; the combined feature is called Sagittarius-Carina arm.

See also: → Carina; → arm.

A → spiral arm in the Milky Way galaxy seen at its best in the → constellation → Carina, but also crossing the constellations → Vela,
→ Crux, and → Centaurus. It may be a continuation of the → Sagittarius arm; the combined feature is called Sagittarius-Carina arm.

See also: → Carina; → arm.

One of the most prominent → massive star formation regions of the → Milky Way, also known as NGC 3372. It is associated with a giant → H II region of the same name, which spans about 4 square degrees on the sky and is split by a remarkable V-shaped → dust lane. The Carina Nebula harbors several → star clusters, mainly
→ Trumpler 14, → Trumpler 16, and Collinder 228, including
more than 60 known → O-type stars in addition to the extreme → LBV star → Eta Carinae. This gas and dust complex is associated with a → giant molecular cloud extending over about 130 pc. Large cavities within the molecular cloud are supposed to be carved out by the massive star clusters. There are also several → Herbig-Haro objects and → bipolar outflows.

See also: → Carina; → nebula.

One of the most prominent → massive star formation regions of the → Milky Way, also known as NGC 3372. It is associated with a giant → H II region of the same name, which spans about 4 square degrees on the sky and is split by a remarkable V-shaped → dust lane. The Carina Nebula harbors several → star clusters, mainly
→ Trumpler 14, → Trumpler 16, and Collinder 228, including
more than 60 known → O-type stars in addition to the extreme → LBV star → Eta Carinae. This gas and dust complex is associated with a → giant molecular cloud extending over about 130 pc. Large cavities within the molecular cloud are supposed to be carved out by the massive star clusters. There are also several → Herbig-Haro objects and → bipolar outflows.

See also: → Carina; → nebula.

The fourteenth of Jupiter’s known satellites; 40 km in size; → retrograde orbit. It was discovered by Nicholson in 1938.

Etymology (EN): In Gk mythology, Carme was a wife of Zeus, and the mother of
Britomartis, a Cretan goddess.

The fourteenth of Jupiter’s known satellites; 40 km in size; → retrograde orbit. It was discovered by Nicholson in 1938.

Etymology (EN): In Gk mythology, Carme was a wife of Zeus, and the mother of
Britomartis, a Cretan goddess.

An experiment devised to produce → interference patterns from a beam of helium atoms passing through two
adjacent apertures, as in → Young’s experiment.

See also: Named after O. Carnal and J. Mlynek, who first carried out this experiment in 1991 (Phys. Rev. Lett. 66, 2689); → experiment.

An experiment devised to produce → interference patterns from a beam of helium atoms passing through two
adjacent apertures, as in → Young’s experiment.

See also: Named after O. Carnal and J. Mlynek, who first carried out this experiment in 1991 (Phys. Rev. Lett. 66, 2689); → experiment.

A → cyclic process comprising a sequence of → isothermal and → adiabatic expansions and compressions that bring a system back to its initial state.

See also: Nicolas Léonard Sadi Carnot (1796-1832), a French physicist and military engineer who, in his 1824 Reflections on the Motive Power of Fire, gave the first successful theoretical account of heat engines; → cycle.

A → cyclic process comprising a sequence of → isothermal and → adiabatic expansions and compressions that bring a system back to its initial state.

See also: Nicolas Léonard Sadi Carnot (1796-1832), a French physicist and military engineer who, in his 1824 Reflections on the Motive Power of Fire, gave the first successful theoretical account of heat engines; → cycle.

1. An atom or molecule responsible for an unidentified spectral feature, such as a → diffuse interstellar band.
   

2. Same as → charge carrier.
   

3. In radio or television transmission, an → electromagnetic wave whose → amplitude, → frequency, or → phase is to be varied or → modulated to transmit a signal.

Etymology (EN): Carrier, from v. carry, from M.E. carien, from O. Norm-Fr. carier “to transport in a vehicle,” from carre “cart,” from L. carrum, carrus “two-wheeled wagon,” from Gaul. karros, from PIE *krsos, from base *kers- “to run.”

Etymology (PE): Barandé “carrier,” from bordan “to carry,” Mid.Pers. burdan, O.Pers./Av. bar- “to bear, carry,” Av. barəθre “to bear (infinitive),” barəθri “a female that bears (children), a mother,” Skt. bharati “he carries,” Gk. pherein, P.Gmc. *beranan, O.H.G. beran, Goth. bairan “to carry,” O.E. beran “bear, bring, wear,” PIE root *bher-; “to carry.”

1. An atom or molecule responsible for an unidentified spectral feature, such as a → diffuse interstellar band.
   

2. Same as → charge carrier.
   

3. In radio or television transmission, an → electromagnetic wave whose → amplitude, → frequency, or → phase is to be varied or → modulated to transmit a signal.

Etymology (EN): Carrier, from v. carry, from M.E. carien, from O. Norm-Fr. carier “to transport in a vehicle,” from carre “cart,” from L. carrum, carrus “two-wheeled wagon,” from Gaul. karros, from PIE *krsos, from base *kers- “to run.”

Etymology (PE): Barandé “carrier,” from bordan “to carry,” Mid.Pers. burdan, O.Pers./Av. bar- “to bear, carry,” Av. barəθre “to bear (infinitive),” barəθri “a female that bears (children), a mother,” Skt. bharati “he carries,” Gk. pherein, P.Gmc. *beranan, O.H.G. beran, Goth. bairan “to carry,” O.E. beran “bear, bring, wear,” PIE root *bher-; “to carry.”

A system for counting rotations of the Sun based on the mean → synodic rotation period of the Sun. Initially, Lord Carrington determined the solar rotation rate by watching low-latitude → sunspots. He defined a fixed solar coordinate system that rotates in a sidereal frame exactly once every 25.38 days. This means that the solar rotation period, as viewed from the Earth, is assumed to be constant. However, the synodic rotation rate varies during the year because of the changing speed of the Earth in its orbit and the mean synodic period is about 27.2753 days. Carrington rotation number 1 began on November 9, 1853.

See also: Named for Richard C. Harrington (1826-1875), British astronomer, who initiated the system; → rotation.

A system for counting rotations of the Sun based on the mean → synodic rotation period of the Sun. Initially, Lord Carrington determined the solar rotation rate by watching low-latitude → sunspots. He defined a fixed solar coordinate system that rotates in a sidereal frame exactly once every 25.38 days. This means that the solar rotation period, as viewed from the Earth, is assumed to be constant. However, the synodic rotation rate varies during the year because of the changing speed of the Earth in its orbit and the mean synodic period is about 27.2753 days. Carrington rotation number 1 began on November 9, 1853.

See also: Named for Richard C. Harrington (1826-1875), British astronomer, who initiated the system; → rotation.

Of or relating to René → Descartes, his mathematical system, or his philosophy, especially with regard to its emphasis on logical analysis and its mechanistic interpretation of physical nature. → Cartesian coordinates; → Cartesian vortex theory.

See also: From L. Cartesianus, from Cartesius, Latinized form of the name of French philosopher and mathematician René Descartes (1596-1650), + suffix -ian.

Of or relating to René → Descartes, his mathematical system, or his philosophy, especially with regard to its emphasis on logical analysis and its mechanistic interpretation of physical nature. → Cartesian coordinates; → Cartesian vortex theory.

See also: From L. Cartesianus, from Cartesius, Latinized form of the name of French philosopher and mathematician René Descartes (1596-1650), + suffix -ian.

A → coordinate system in which the position of a point is specified by two (in a plane) or three (in 3-dimensional space) → real numbers representing the distances from two perpendicular axes or from three perpendicular planes, respectively. René Descartes (1596-1650) introduced the coordinates system in his La Géométrie in 1637.

See also: → Cartesian; → coordinate.

A → coordinate system in which the position of a point is specified by two (in a plane) or three (in 3-dimensional space) → real numbers representing the distances from two perpendicular axes or from three perpendicular planes, respectively. René Descartes (1596-1650) introduced the coordinates system in his La Géométrie in 1637.

See also: → Cartesian; → coordinate.

A mechanical model put forward before Newton’s theory of gravity to explain the revolution of the planets around the Sun. Descartes in his 1644 Principia Philosophiae
postulated that the space between the Sun and the planets is filled with matter in the form of a fluid. The fluid rotates in countless whirlpools, one for each planet, thus carrying the planets along in their flow. The vortices vary in size and are contiguous as well as nested. Descartes believed that two objects can exert force on each other only when they are in physical contact. This is why he postulated that space is filled with matter. Newton refuted the vortex theory, using the principle of → action at a distance on which relies his → law of universal gravitation.

See also: → Cartesian; → vortex; → theory.

A mechanical model put forward before Newton’s theory of gravity to explain the revolution of the planets around the Sun. Descartes in his 1644 Principia Philosophiae
postulated that the space between the Sun and the planets is filled with matter in the form of a fluid. The fluid rotates in countless whirlpools, one for each planet, thus carrying the planets along in their flow. The vortices vary in size and are contiguous as well as nested. Descartes believed that two objects can exert force on each other only when they are in physical contact. This is why he postulated that space is filled with matter. Newton refuted the vortex theory, using the principle of → action at a distance on which relies his → law of universal gravitation.

See also: → Cartesian; → vortex; → theory.

A galaxy with a striking ring-like feature lying about 400 million → light-years away in the → constellation  → Sculptor. The ring-like structure, over 100,000 light-years in diameter, is composed of regions of → star formation filled with very bright, → massive stars. The shape results from collision with another smaller galaxy.

Etymology (EN): Cartwheel, from cart from O.N. kartr;
→ wheel; → galaxy.

Etymology (PE): Kahkašân, → galaxy. Carx-e arrâbé “cartwheel,” from carx, → wheel

• arrâbé “cart, chariot,” maybe related to Mid.Pers. ras, ray “wheel,” O.Pers./Av. raθa- “wheel,” Khotanese rrha- “car,” Skt. ratha- “wheel,” L. rota “wheel,” PIE base *rotos “wheel.”

A galaxy with a striking ring-like feature lying about 400 million → light-years away in the → constellation  → Sculptor. The ring-like structure, over 100,000 light-years in diameter, is composed of regions of → star formation filled with very bright, → massive stars. The shape results from collision with another smaller galaxy.

Etymology (EN): Cartwheel, from cart from O.N. kartr;
→ wheel; → galaxy.

Etymology (PE): Kahkašân, → galaxy. Carx-e arrâbé “cartwheel,” from carx, → wheel

• arrâbé “cart, chariot,” maybe related to Mid.Pers. ras, ray “wheel,” O.Pers./Av. raθa- “wheel,” Khotanese rrha- “car,” Skt. ratha- “wheel,” L. rota “wheel,” PIE base *rotos “wheel.”

1. A waterfall or a succession of small waterfalls.
   
2. A succession of stages or processes, as in → cascade shower, → cascade error, → cascade transition.

Etymology (EN): From Fr., from It. cascata “waterfall,” from cascare “to fall,” from V.L. *casicare, from L. casum, p.p. of cadere “to fall,” → case.

Etymology (PE): Âbšâr, from âb “water,” → Aquarius, + šâr “pouring of water and liquids, waterfall;” peyšâr “waterfall succession,” from pey “step, succession,” as in peyâpey, + šâr. This word maybe related to Skt. sar- “to flow, run, hurry,” Gk. iallo “I send out,” L. salio “I jump.” It may also be variant of Mod.Pers. cal-, calidan “to walk, be going,” car-, caridan “to pasture, graze,” Av. car- “to come and go,” Skt. cari- “to move, walk, wander.”

1. A waterfall or a succession of small waterfalls.
   
2. A succession of stages or processes, as in → cascade shower, → cascade error, → cascade transition.

Etymology (EN): From Fr., from It. cascata “waterfall,” from cascare “to fall,” from V.L. *casicare, from L. casum, p.p. of cadere “to fall,” → case.

Etymology (PE): Âbšâr, from âb “water,” → Aquarius, + šâr “pouring of water and liquids, waterfall;” peyšâr “waterfall succession,” from pey “step, succession,” as in peyâpey, + šâr. This word maybe related to Skt. sar- “to flow, run, hurry,” Gk. iallo “I send out,” L. salio “I jump.” It may also be variant of Mod.Pers. cal-, calidan “to walk, be going,” car-, caridan “to pasture, graze,” Av. car- “to come and go,” Skt. cari- “to move, walk, wander.”

An error that amplifies as the process of calculation goes on.

See also: → cascade; → error.

An error that amplifies as the process of calculation goes on.

See also: → cascade; → error.

Multiple generations of secondary cosmic rays when the primary particles produce a succession of secondaries which have the same effects as the primary.

See also: → cascade; → shower.

Multiple generations of secondary cosmic rays when the primary particles produce a succession of secondaries which have the same effects as the primary.

See also: → cascade; → shower.

A photon generation mechanism in an atom in which a transition initiates a series of secondary transitions from lower electronic levels.

See also: → cascade; → transition.

A photon generation mechanism in an atom in which a transition initiates a series of secondary transitions from lower electronic levels.

See also: → cascade; → transition.

1. An instance of the occurrence, or existence of something.
   

2. A set of circumstances or conditions.
   

3. Grammar: An inflectional form of a noun, pronoun, or adjective indicating its grammatical relation to other words.

Etymology (EN): M.E. cas, from O.Fr. cas “an event, happening, situation,” from L. casus “a chance, occasion, opportunity; accident,” literally “a falling,” from cadere “to fall, sink, settle down” (Sp. caer, caida); Sp. caso; It. caso; Port. caso;
PIE root *kad- “to fall;” cf. Skt. śad- “to fall down;” Pers. kat, as below.

Etymology (PE): Kâté, from Iranian dialects/languages kat- “to fall” (with extension of the first vowel), as Laki: katen “to fall,” kat “he/she fell,” beko “fall!” (an insult); katyâ “fallen;” Lori: kat “event, error;” Kurd. (Soriani): kawtin “to fall, befall,” kett “fallen;” Kurd. (Kurmanji): da.ketin “to fall down;” Lârestâni: kata “to fall;” Garkuyeyi: darkat, varkat “he/she fell (sudden death);” Gilaki (Langarud, Tâleš): katan “to fall,” bakatam “I fell,” dakatan “to fall (in a marsh, in a pit),” vakatan “to fall from tiredness, be exhausted,” fakatan “to fall from (i.e., lose) reputation;” Tabari: dakətə “fallen,” dakətən “to crash down,” dakət.gu “stray cow;” Proto-Iranian *kat- “to fall;” cf. L. cadere, as above. Alternatively, from Proto-Ir. *kap-, *kaf- “to (be)fall, strike (down);” cf. Baluci kapag, kafag “to fall,” kapt “(past tense) fell;” Bampuri kapte “fallen;” Kurd. (Sanandaj) kaften “to fall;” Gilaki jekaftan “to fall;” Nâyini derkaftan “to fall down.”

1. An instance of the occurrence, or existence of something.
   

2. A set of circumstances or conditions.
   

3. Grammar: An inflectional form of a noun, pronoun, or adjective indicating its grammatical relation to other words.

Etymology (EN): M.E. cas, from O.Fr. cas “an event, happening, situation,” from L. casus “a chance, occasion, opportunity; accident,” literally “a falling,” from cadere “to fall, sink, settle down” (Sp. caer, caida); Sp. caso; It. caso; Port. caso;
PIE root *kad- “to fall;” cf. Skt. śad- “to fall down;” Pers. kat, as below.

Etymology (PE): Kâté, from Iranian dialects/languages kat- “to fall” (with extension of the first vowel), as Laki: katen “to fall,” kat “he/she fell,” beko “fall!” (an insult); katyâ “fallen;” Lori: kat “event, error;” Kurd. (Soriani): kawtin “to fall, befall,” kett “fallen;” Kurd. (Kurmanji): da.ketin “to fall down;” Lârestâni: kata “to fall;” Garkuyeyi: darkat, varkat “he/she fell (sudden death);” Gilaki (Langarud, Tâleš): katan “to fall,” bakatam “I fell,” dakatan “to fall (in a marsh, in a pit),” vakatan “to fall from tiredness, be exhausted,” fakatan “to fall from (i.e., lose) reputation;” Tabari: dakətə “fallen,” dakətən “to crash down,” dakət.gu “stray cow;” Proto-Iranian *kat- “to fall;” cf. L. cadere, as above. Alternatively, from Proto-Ir. *kap-, *kaf- “to (be)fall, strike (down);” cf. Baluci kapag, kafag “to fall,” kapt “(past tense) fell;” Bampuri kapte “fallen;” Kurd. (Sanandaj) kaften “to fall;” Gilaki jekaftan “to fall;” Nâyini derkaftan “to fall down.”

A small attractive force that appears between two close parallel uncharged plates in a vacuum. It is due to quantum vacuum fluctuations of the electromagnetic field. According to the quantum theory, the vacuum contains → virtual particles which are in a continuous state of fluctuation. Because the distance between the plates is very small, not every possible wavelength can exist in the space between the two plates, quite in contrast to the surrounding vacuum. The energy density decreases as the plates are moved closer, creating a negative pressure which pulls the plates together. The first successfully measurement of the effect was by Steve Lamoreaux in 1997. A more recent experiment in 2002 used a polystyrene sphere 200 μm in diameter coated in gold or aluminium. This was brought to within 0.1 μm of a flat disk coated with the same metals. The resulting attraction between them was monitored by the deviation of a laser beam. The Casimir force was measured to within 1% of the expected theoretical value.

See also: After the Dutch physicist Hendrik Casimir (1909-2000), who predicted the phenomenon in 1948; → effect.

A small attractive force that appears between two close parallel uncharged plates in a vacuum. It is due to quantum vacuum fluctuations of the electromagnetic field. According to the quantum theory, the vacuum contains → virtual particles which are in a continuous state of fluctuation. Because the distance between the plates is very small, not every possible wavelength can exist in the space between the two plates, quite in contrast to the surrounding vacuum. The energy density decreases as the plates are moved closer, creating a negative pressure which pulls the plates together. The first successfully measurement of the effect was by Steve Lamoreaux in 1997. A more recent experiment in 2002 used a polystyrene sphere 200 μm in diameter coated in gold or aluminium. This was brought to within 0.1 μm of a flat disk coated with the same metals. The resulting attraction between them was monitored by the deviation of a laser beam. The Casimir force was measured to within 1% of the expected theoretical value.

See also: After the Dutch physicist Hendrik Casimir (1909-2000), who predicted the phenomenon in 1948; → effect.

The main focus in → Cassegrain telescope.

See also: → Cassegrain telescope; → focus.

The main focus in → Cassegrain telescope.

See also: → Cassegrain telescope; → focus.

A reflecting telescope whose primary mirror has a hole bored through the center to allow the reflected light from the convex secondary mirror be focused beyond the back end of the tube.

Etymology (EN): Cassegrain, named after the French priest and school teacher Laurent Cassegrain (1629-1693), who invented this system in 1672;
→ telescope.

A reflecting telescope whose primary mirror has a hole bored through the center to allow the reflected light from the convex secondary mirror be focused beyond the back end of the tube.

Etymology (EN): Cassegrain, named after the French priest and school teacher Laurent Cassegrain (1629-1693), who invented this system in 1672;
→ telescope.

The main dark gap, 4,700 km wide, which divides Saturn’s outermost A and B rings.

See also: Named after Jean-Dominique Cassini (1625-1712), French astronomer of Italian origin, who discovered the division in 1675; → division.

The main dark gap, 4,700 km wide, which divides Saturn’s outermost A and B rings.

See also: Named after Jean-Dominique Cassini (1625-1712), French astronomer of Italian origin, who discovered the division in 1675; → division.

A state characterizing a system which obeys → Cassini’s laws.

See also: → Cassini’s law; → state.

A state characterizing a system which obeys → Cassini’s laws.

See also: → Cassini’s law; → state.

A joint endeavor of → NASA, → ESA, and the Italian space agency that sent a spacecraft to study the planet → Saturn and its system, including → Saturn’s rings and its natural satellites. The spacecraft was 6.70 m × 4 m × 4 m and weighed about 6 tons. Cassini drew its electric power from the heat generated by the decay of 33 kg of → plutonium-238. The spacecraft carried 12 sophisticated observation and measuring instruments. Cassini-Huygens was launched on 15 October 1997. It used several → gravity assist manoeuvres to boost itself toward Saturn. It flew past Venus two times (April 1998 and June 1999), made → flybys of Earth (August 1999), and f
Jupiter (December 2000). After 6 years and 8 months, covering about 8 billion km it entered Saturn orbit on July 1, 2004. It stayed there for 13 years and made detailed observations of the planet, its rings, and its moons.

A scientific probe called Huygens was released on December 25, 2004 from the main spacecraft to parachute through the atmosphere to the surface of Saturn’s largest and most interesting moon, → Titan.

The data that Huygens transmitted during its final descent and for 72 minutes from the surface included 350 pictures that showed a shoreline with erosion features and a river delta.

Cassini continued to orbit Saturn and complete many flybys of Saturn’s moons. A particularly exciting discovery during its mission was that of → geysers of water ice and organic molecules at the south pole of → Enceladus, which erupt from an underground global ocean that could be a possible environment for life. Cassini’s radar mapped much of Titan’s surface and found large lakes of liquid → methane. Cassini also discovered six new moons and two new rings of Saturn. The mission was ended on September 15, 2017 when the spacecraft was crashed into Saturn’s body and destroyed.

This was the best way to avoid contaminating Saturn’s moons with possible Earth microbes, because the moons may have the potential to support life.

See also: Named after two famous scientists. The Saturn orbiter is named after the Italian/french astronomer Jean-Domenique Cassini, who discovered the Saturnian satellites → Iapetus in 1671, → Rhea in 1672, and both → Tethys and → Dione in 1684. In 1675 he discovered what is known today as the → Cassini division, the narrow gap separating Saturn’s rings into two parts. The Titan probe was named Huygens in honor of the Dutch scientist, Christiaan Huygens, who discovered Titan in 1655.

A joint endeavor of → NASA, → ESA, and the Italian space agency that sent a spacecraft to study the planet → Saturn and its system, including → Saturn’s rings and its natural satellites. The spacecraft was 6.70 m × 4 m × 4 m and weighed about 6 tons. Cassini drew its electric power from the heat generated by the decay of 33 kg of → plutonium-238. The spacecraft carried 12 sophisticated observation and measuring instruments. Cassini-Huygens was launched on 15 October 1997. It used several → gravity assist manoeuvres to boost itself toward Saturn. It flew past Venus two times (April 1998 and June 1999), made → flybys of Earth (August 1999), and f
Jupiter (December 2000). After 6 years and 8 months, covering about 8 billion km it entered Saturn orbit on July 1, 2004. It stayed there for 13 years and made detailed observations of the planet, its rings, and its moons.

A scientific probe called Huygens was released on December 25, 2004 from the main spacecraft to parachute through the atmosphere to the surface of Saturn’s largest and most interesting moon, → Titan.

The data that Huygens transmitted during its final descent and for 72 minutes from the surface included 350 pictures that showed a shoreline with erosion features and a river delta.

Cassini continued to orbit Saturn and complete many flybys of Saturn’s moons. A particularly exciting discovery during its mission was that of → geysers of water ice and organic molecules at the south pole of → Enceladus, which erupt from an underground global ocean that could be a possible environment for life. Cassini’s radar mapped much of Titan’s surface and found large lakes of liquid → methane. Cassini also discovered six new moons and two new rings of Saturn. The mission was ended on September 15, 2017 when the spacecraft was crashed into Saturn’s body and destroyed.

This was the best way to avoid contaminating Saturn’s moons with possible Earth microbes, because the moons may have the potential to support life.

See also: Named after two famous scientists. The Saturn orbiter is named after the Italian/french astronomer Jean-Domenique Cassini, who discovered the Saturnian satellites → Iapetus in 1671, → Rhea in 1672, and both → Tethys and → Dione in 1684. In 1675 he discovered what is known today as the → Cassini division, the narrow gap separating Saturn’s rings into two parts. The Titan probe was named Huygens in honor of the Dutch scientist, Christiaan Huygens, who discovered Titan in 1655.

Any of the three empirical laws governing the rotational dynamics of the → Moon:

1. The Moon rotates uniformly about its polar axis with a → rotational period equal to the mean → sidereal period of its orbit about the Earth.
   

2. The → inclination of the Moon’s equator to the → ecliptic is a constant angle approximately 1.5°.
   

3. The → ascending node of the lunar orbit on the ecliptic coincides with the → descending node of the lunar equator on the ecliptic. This law could also be expressed as: the spin axis and the normals to the ecliptic and orbit plane remain coplanar
   (Noyelles, 2009, Icarus, 202, 225).

See also: Named after Jean-Dominique Cassini (1625-1712), French astronomer of Italian origin, who established these laws in 1693 (Traité de l’origine et du progrès de l’astronomie), ; → law.

Any of the three empirical laws governing the rotational dynamics of the → Moon:

1. The Moon rotates uniformly about its polar axis with a → rotational period equal to the mean → sidereal period of its orbit about the Earth.
   

2. The → inclination of the Moon’s equator to the → ecliptic is a constant angle approximately 1.5°.
   

3. The → ascending node of the lunar orbit on the ecliptic coincides with the → descending node of the lunar equator on the ecliptic. This law could also be expressed as: the spin axis and the normals to the ecliptic and orbit plane remain coplanar
   (Noyelles, 2009, Icarus, 202, 225).