An Etymological Dictionary of Astronomy and Astrophysics

A chemical compound that contains the → cyano radical, -CN. Most cyanides are highly toxic.

See also: → cyano-; → -ide.

A chemical compound that contains the → cyano radical, -CN. Most cyanides are highly toxic.

See also: → cyano-; → -ide.

A diatomic chemical radical composed of carbon and nitrogen atoms.
The triple bonds of C to H leave one electron available,
which makes the CN radical very reactive. Organic molecules with the -CN group are potential sources of → prebiotic amino acids. Same as the → CN molecule. The CN radical was first identified by Gay-Lussac, who in 1815 published an extensive study of the derivatives of prussic acid (→ hydrogen cyanide). He showed that the cyano radical remained intact throughout a series of chemical transformations. Also called cyanogen radical.

See also: → cyano-; → radical.

A diatomic chemical radical composed of carbon and nitrogen atoms.
The triple bonds of C to H leave one electron available,
which makes the CN radical very reactive. Organic molecules with the -CN group are potential sources of → prebiotic amino acids. Same as the → CN molecule. The CN radical was first identified by Gay-Lussac, who in 1815 published an extensive study of the derivatives of prussic acid (→ hydrogen cyanide). He showed that the cyano radical remained intact throughout a series of chemical transformations. Also called cyanogen radical.

See also: → cyano-; → radical.

1. A combining form meaning “blue, dark blue,” used in the formation of compound words. Also cyan- before a vowel.
   

2. A combining form representing → cyanide in the formation of chemical compounds.

See also: From Gk. kyanos “dark blue, lapis lazuli,” because of its presence in the Prussian blue, Fe₇(CN)₁₈, a dye which was first accidentally made around 1706, by heating substances containing iron and carbon and nitrogen.

1. A combining form meaning “blue, dark blue,” used in the formation of compound words. Also cyan- before a vowel.
   

2. A combining form representing → cyanide in the formation of chemical compounds.

See also: From Gk. kyanos “dark blue, lapis lazuli,” because of its presence in the Prussian blue, Fe₇(CN)₁₈, a dye which was first accidentally made around 1706, by heating substances containing iron and carbon and nitrogen.

1. A colorless, very poisonous, flammable gas with a smell of bitter almonds. Chemical formula: C₂N₂. It was discovered by Louis Joseph Gay-Lussac (1778-1850) in 1848.
   

2. A univalent radical, CN, found in simple and complex cyanide compounds. CN exists in → interstellar medium and is one of the main molecules detected in → comets. It has energy levels at 113 and 227 GHz (2.6 and 1.3 mm wavelength) above the ground level.

See also: → cyano- + → -gen.

1. A colorless, very poisonous, flammable gas with a smell of bitter almonds. Chemical formula: C₂N₂. It was discovered by Louis Joseph Gay-Lussac (1778-1850) in 1848.
   

2. A univalent radical, CN, found in simple and complex cyanide compounds. CN exists in → interstellar medium and is one of the main molecules detected in → comets. It has energy levels at 113 and 227 GHz (2.6 and 1.3 mm wavelength) above the ground level.

See also: → cyano- + → -gen.

An → absorption band of molecular origin
characterizing the spectra of → late-type stars (G0 and later, e.g. → S star). → Cyanogen absorption is an important → luminosity criterion for → low-mass stars, and is more pronounced in → giant stars than in → dwarf stars of the same → spectral type.

See also: → cyanogen; → band.

An → absorption band of molecular origin
characterizing the spectra of → late-type stars (G0 and later, e.g. → S star). → Cyanogen absorption is an important → luminosity criterion for → low-mass stars, and is more pronounced in → giant stars than in → dwarf stars of the same → spectral type.

See also: → cyanogen; → band.

1. A sequence of changes that are repeated regularly, such as revolution, rotation, vibration, oscillation, wave motion.
   

2. One complete set of changes in the value of a → periodic function during one period.
   

3. A period of time at the end of which an event or sequence of events are repeated.
   → carbon cycle, → Carnot cycle, → CNO cycle, → cycle shape, → hydrologic cycle, → Metonic cycle, → Milankovich cycle, → solar activity cycle, → solar cycle, → solar magnetic cycle, → sunspot cycle, → epicycle, → recycle.
   

4. In → graph theory, a closed → path with at least one → edge.

Etymology (EN): From L.L. cyclus, from Gk. kyklos “circle, wheel,” from PIE base *kw(e)-kwl-o- “wheel, circle,” from *kwel- “to turn, move around, sojourn, dwell,” (cf. Av. caxra- “wheel,” caraiti “he moves, approaches;”
Mod.Pers. carx “wheel;” Skt. cakra- “wheel, circle; cycle,” carati “he moves, wanders;” Gk. polos “axis of a sphere,” polein “move around;” L. colere “to dwell in, to cultivate, move around,” colonus “farmer, settler;” O.E. hweol “wheel;” Rus. koleso “awheel”).

Etymology (PE): Carx “every thing performing a circulatory motion; a wheel; a cart,” Mid.Pers. chr “wheel,” Parthian cxr “wheel,” Ossetic, Khotanese calx “wheel,” Av. caxra- “wheel,” cognate with Gk. kyklos “circle, wheel,” as above. Carxé from carx + nuance suffix -é.

1. A sequence of changes that are repeated regularly, such as revolution, rotation, vibration, oscillation, wave motion.
   

2. One complete set of changes in the value of a → periodic function during one period.
   

3. A period of time at the end of which an event or sequence of events are repeated.
   → carbon cycle, → Carnot cycle, → CNO cycle, → cycle shape, → hydrologic cycle, → Metonic cycle, → Milankovich cycle, → solar activity cycle, → solar cycle, → solar magnetic cycle, → sunspot cycle, → epicycle, → recycle.
   

4. In → graph theory, a closed → path with at least one → edge.

Etymology (EN): From L.L. cyclus, from Gk. kyklos “circle, wheel,” from PIE base *kw(e)-kwl-o- “wheel, circle,” from *kwel- “to turn, move around, sojourn, dwell,” (cf. Av. caxra- “wheel,” caraiti “he moves, approaches;”
Mod.Pers. carx “wheel;” Skt. cakra- “wheel, circle; cycle,” carati “he moves, wanders;” Gk. polos “axis of a sphere,” polein “move around;” L. colere “to dwell in, to cultivate, move around,” colonus “farmer, settler;” O.E. hweol “wheel;” Rus. koleso “awheel”).

Etymology (PE): Carx “every thing performing a circulatory motion; a wheel; a cart,” Mid.Pers. chr “wheel,” Parthian cxr “wheel,” Ossetic, Khotanese calx “wheel,” Av. caxra- “wheel,” cognate with Gk. kyklos “circle, wheel,” as above. Carxé from carx + nuance suffix -é.

A graph displaying the average → sunspot number over each → sunspot cycle. It presents a shape of skewed → Gaussian: the rise to maximum is faster than the decline to minimum.

See also: → cycle; → shape.

A graph displaying the average → sunspot number over each → sunspot cycle. It presents a shape of skewed → Gaussian: the rise to maximum is faster than the decline to minimum.

See also: → cycle; → shape.

Of, pertaining to, or constituting a cycle or cycles.

See also: → cycle; → -ic.

Of, pertaining to, or constituting a cycle or cycles.

See also: → cycle; → -ic.

Same as → ignorable coordinate.

See also: → cyclic; → coordinate.

Same as → ignorable coordinate.

See also: → cyclic; → coordinate.

A group in which each element can be expressed as a power of any other element.

See also: → cyclic; → group.

A group in which each element can be expressed as a power of any other element.

See also: → cyclic; → group.

Any sequence of changes in a → thermodynamic system that returns the system into its → initial  → state.

See also: → cyclic; → process.

Any sequence of changes in a → thermodynamic system that returns the system into its → initial  → state.

See also: → cyclic; → process.

A quadrilateral in which all four vertices lie on the circumference of a circle.

See also: → cyclic; → quadrilateral.

A quadrilateral in which all four vertices lie on the circumference of a circle.

See also: → cyclic; → quadrilateral.

The curve traced by a point on the circumference of a circle that rolls along a straight line. The cycloid has a → cusp at every point where it touches the straight line. The distance between cusps is 2πR, where R is the radius of the circle.

Etymology (EN): Cycloid, from Gk. kykloeides “circular,” fr. kyklos “circle,” → cycle + eides “form,” → -oid.

Etymology (PE): Carxzâd, from carx “wheel, circle,” → cycle + zâd “produced, created, born,” from zâdan “give birth” (Av. zan- “to bear, give birth to a child, be born,” infinitive zazâite, zâta- “born,” cf. Skt. janati “begets, bears,” Gk. gignesthai “to become, happen” L. gignere “to beget,” gnasci “to be born,” PIE base *gen- “to give birth, beget”).

The curve traced by a point on the circumference of a circle that rolls along a straight line. The cycloid has a → cusp at every point where it touches the straight line. The distance between cusps is 2πR, where R is the radius of the circle.

Etymology (EN): Cycloid, from Gk. kykloeides “circular,” fr. kyklos “circle,” → cycle + eides “form,” → -oid.

Etymology (PE): Carxzâd, from carx “wheel, circle,” → cycle + zâd “produced, created, born,” from zâdan “give birth” (Av. zan- “to bear, give birth to a child, be born,” infinitive zazâite, zâta- “born,” cf. Skt. janati “begets, bears,” Gk. gignesthai “to become, happen” L. gignere “to beget,” gnasci “to be born,” PIE base *gen- “to give birth, beget”).

Any circulatory wind system in the atmosphere in which the motion is anticlockwise in the northern hemisphere (that is in the same sense as that of Earth) and clockwise in the southern hemisphere, around a center of low pressure.

Etymology (EN): From Gk. kyklon “moving in a circle, whirling around,” pr.p. of kykloun “move in a circle, whirl,” from kyklos “circle,” cognate with Pers. carx→ cycle.

Etymology (PE): Carxand “moving in a circle,” from carxidan→ rotate, from carx, → cycle.

Any circulatory wind system in the atmosphere in which the motion is anticlockwise in the northern hemisphere (that is in the same sense as that of Earth) and clockwise in the southern hemisphere, around a center of low pressure.

Etymology (EN): From Gk. kyklon “moving in a circle, whirling around,” pr.p. of kykloun “move in a circle, whirl,” from kyklos “circle,” cognate with Pers. carx→ cycle.

Etymology (PE): Carxand “moving in a circle,” from carxidan→ rotate, from carx, → cycle.

Having a sense of rotation about the local vertical the same as that of the Earth’s rotation. More specifically, as viewed from above, → counterclockwise in the Northern Hemisphere, → clockwise in the Southern Hemisphere, and undefined at the equator. The opposite of → anticyclonic (Meteorology Glossary, American Meteorological Society).

See also: → cyclone; → -ic.

Having a sense of rotation about the local vertical the same as that of the Earth’s rotation. More specifically, as viewed from above, → counterclockwise in the Northern Hemisphere, → clockwise in the Southern Hemisphere, and undefined at the equator. The opposite of → anticyclonic (Meteorology Glossary, American Meteorological Society).

See also: → cyclone; → -ic.

An → accelerator in which charged subatomic particles generated at a central source are accelerated to acquire energies up to several tens of millions of → electron-volts. The cyclotron consists of two flat, semicircular metal boxes or electrodes, called dees or D’s because of their shape. An alternating electric field between the dees continuously accelerates the particles from one dee to the other, while the magnetic field bends their direction guiding them in a circular path. As the speed of the particles increases, so does the radius of their path, and the particles spiral outward. See also → cyclotron frequency, → synchrotron.

See also: From cyclo- a combining form meaning → cycle

• → -tron.

An → accelerator in which charged subatomic particles generated at a central source are accelerated to acquire energies up to several tens of millions of → electron-volts. The cyclotron consists of two flat, semicircular metal boxes or electrodes, called dees or D’s because of their shape. An alternating electric field between the dees continuously accelerates the particles from one dee to the other, while the magnetic field bends their direction guiding them in a circular path. As the speed of the particles increases, so does the radius of their path, and the particles spiral outward. See also → cyclotron frequency, → synchrotron.

See also: From cyclo- a combining form meaning → cycle

• → -tron.

The frequency with which a → non-relativistic particle of charge q and mass m turns in a cyclotron with
→ uniform magnetic field B. The equality of the → centripetal force to the → Lorentz force leads to the expression: by: f_cycl = qB/2πm. For → relativistic case, the frequency is smaller and is called
→ synchrotron frequency.

See also: → cyclotron; → frequency.

The frequency with which a → non-relativistic particle of charge q and mass m turns in a cyclotron with
→ uniform magnetic field B. The equality of the → centripetal force to the → Lorentz force leads to the expression: by: f_cycl = qB/2πm. For → relativistic case, the frequency is smaller and is called
→ synchrotron frequency.

See also: → cyclotron; → frequency.

Same as → Larmor radius.

See also: → cyclotron; → radius.

Same as → Larmor radius.

See also: → cyclotron; → radius.

The Swan. A prominent northern → constellation that lies in the glowing band of the Milky way, east of Lyra and north of Vulpecula, and represents a swan.
The brightest stars of Cygnus form a cross, so it is also known as the Northern Cross. Abbreviation: Cyg, genitive: Cygni.

Etymology (EN): From L. cygnus “swan,” from Gk. kuknos.

Etymology (PE): Mâkiyân “a hen, fowl.”

The Swan. A prominent northern → constellation that lies in the glowing band of the Milky way, east of Lyra and north of Vulpecula, and represents a swan.
The brightest stars of Cygnus form a cross, so it is also known as the Northern Cross. Abbreviation: Cyg, genitive: Cygni.

Etymology (EN): From L. cygnus “swan,” from Gk. kuknos.

Etymology (PE): Mâkiyân “a hen, fowl.”

The strongest extragalactic radio source in the sky approximately 10⁹ light-years away in the → constellation  → Cygnus. Also called 3C 405.

See also: → Cygnus.

The strongest extragalactic radio source in the sky approximately 10⁹ light-years away in the → constellation  → Cygnus. Also called 3C 405.

See also: → Cygnus.

A large supernova remnant in the → constellation  → Cygnus, some 80 light-years across, lying about 2,500 light-years away. The loop is expanding at over 100 km/s and is thought to be about 30 000 years old.

See also: → Cygnus, → loop.

A large supernova remnant in the → constellation  → Cygnus, some 80 light-years across, lying about 2,500 light-years away. The loop is expanding at over 100 km/s and is thought to be about 30 000 years old.

See also: → Cygnus, → loop.

One of nine → OB associations located in the Cygnus → constellation. The central association, → Cygnus OB2, is the most famous and the youngest of the Cygnus region. (L. Mahy et al. 2013, astro-ph/1301.0500 and references therein).

See also: → Cygnus; → OB star; → association.

One of nine → OB associations located in the Cygnus → constellation. The central association, → Cygnus OB2, is the most famous and the youngest of the Cygnus region. (L. Mahy et al. 2013, astro-ph/1301.0500 and references therein).

See also: → Cygnus; → OB star; → association.

The nearest example of a → massive star region of → star formation, containing 65 known → O-type stars and hundreds of → B-type stars. Cygnus OB2 lies at a distance of 1.45 → kpc. It is the central association, the most famous, and one of the youngest of the Cygnus region. Cyg OB2 possibly has two → populations with ages of 3.5-5 Myr, while the → O stars seem to belong to a younger population, aged about 2 Myr.

See also: → Cygnus; → OB association; 2 because there are several OB associations in Cygnus; → Cygnus OB association.

The nearest example of a → massive star region of → star formation, containing 65 known → O-type stars and hundreds of → B-type stars. Cygnus OB2 lies at a distance of 1.45 → kpc. It is the central association, the most famous, and one of the youngest of the Cygnus region. Cyg OB2 possibly has two → populations with ages of 3.5-5 Myr, while the → O stars seem to belong to a younger population, aged about 2 Myr.

See also: → Cygnus; → OB association; 2 because there are several OB associations in Cygnus; → Cygnus OB association.

A → binary system containing one of the best candidates for a → black hole. Cygnus X-1 was discovered as an → X-ray source in 1965. It is one of the brightest X-ray sources on the sky, so that it was detected by the earliest → X-ray observation attempts. This binary system, distant of 2.5 kpc, consists of the O9.7 Iab type → supergiant HDE 226868 and a → compact object orbiting around with a period of 5.6 days. The mass of the unseen companion, significantly larger than 5 → solar masses, suggests that it is a black hole. Focused → wind accretion from a → primary star being extremely close to filling the → Roche lobe drives the powerful source of the X-ray radiation.

See also: → Cygnus.

A → binary system containing one of the best candidates for a → black hole. Cygnus X-1 was discovered as an → X-ray source in 1965. It is one of the brightest X-ray sources on the sky, so that it was detected by the earliest → X-ray observation attempts. This binary system, distant of 2.5 kpc, consists of the O9.7 Iab type → supergiant HDE 226868 and a → compact object orbiting around with a period of 5.6 days. The mass of the unseen companion, significantly larger than 5 → solar masses, suggests that it is a black hole. Focused → wind accretion from a → primary star being extremely close to filling the → Roche lobe drives the powerful source of the X-ray radiation.

See also: → Cygnus.

The surface traced by one side of a rectangle rotating about its parallel side, the latter serving as axis.

Etymology (EN): From Fr. cylindre, from L. cylindrus “roller, cylinder,” from Gk. kylindros “a cylinder, roller, roll,” from kylindein “to roll.”

Etymology (PE): Osotvâné, from sotun “column,” Mid.Pers. stun, from O.Pers. stênâ “column,” Av. stuna-, Skt. sthuna- “column.”

The surface traced by one side of a rectangle rotating about its parallel side, the latter serving as axis.

Etymology (EN): From Fr. cylindre, from L. cylindrus “roller, cylinder,” from Gk. kylindros “a cylinder, roller, roll,” from kylindein “to roll.”

Etymology (PE): Osotvâné, from sotun “column,” Mid.Pers. stun, from O.Pers. stênâ “column,” Av. stuna-, Skt. sthuna- “column.”

Of, pertaining to, or having the form of a cylinder.

See also: From L. cylindricus, from Gk. kylindrikos, see
→ cylinder; → -ic;
→ -al.

Of, pertaining to, or having the form of a cylinder.

See also: From L. cylindricus, from Gk. kylindrikos, see
→ cylinder; → -ic;
→ -al.

A coordinate system for a point in space, using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which a point (P) in space is specified by three numbers ρ, φ, z. The two first numbers, ρ and φ, are → polar coordinates for the vertical projection of P on the xy-plane, and z is the vertical distance of P from the xy-plane.

See also: → cylindrical; → coordinate.

A coordinate system for a point in space, using an origin (O) and three perpendicular axes (Ox, Oy, Oz), in which a point (P) in space is specified by three numbers ρ, φ, z. The two first numbers, ρ and φ, are → polar coordinates for the vertical projection of P on the xy-plane, and z is the vertical distance of P from the xy-plane.

See also: → cylindrical; → coordinate.

A lens in which at least one surface is formed like a portion of a cylinder. Also called astigmatic lens.

See also: → cylinder; → lens.

A lens in which at least one surface is formed like a portion of a cylinder. Also called astigmatic lens.

See also: → cylinder; → lens.

Referring to the Moon.

Etymology (EN): From L. Cynthia “the Moon,” from Gk. Kynthia “woman from Kynthos.” Kynthos was the mountain on Delos on which she and her twin brother Apollo were born.

Etymology (PE): Mâhi, mângi referring to mâh, mâng, → moon.

Referring to the Moon.

Etymology (EN): From L. Cynthia “the Moon,” from Gk. Kynthia “woman from Kynthos.” Kynthos was the mountain on Delos on which she and her twin brother Apollo were born.

Etymology (PE): Mâhi, mângi referring to mâh, mâng, → moon.

Referring to the planet Venus.

Etymology (EN): From Cythera, in Gk. mythology another name of Aphrodite (Roman equivalent Venus), goddess of love and beauty, since she was believed to emerge from the Mediterranean island
Cythera.

Etymology (PE): Nâhidi referring to Nâhid, planet Venus, Mid.Pers. Anahid “immaculate, unstained,” goddess of pure waters and fertility, from Av. arədvi-sûra-anâhita, from arədvi- “increasing, rising,” + sûra- “strong, powerful” (Skt. śūra- “valient, courageous”) + anâhita “unstained,” from an- negation prefix + âhita “spotted.”

Referring to the planet Venus.

Etymology (EN): From Cythera, in Gk. mythology another name of Aphrodite (Roman equivalent Venus), goddess of love and beauty, since she was believed to emerge from the Mediterranean island
Cythera.

Etymology (PE): Nâhidi referring to Nâhid, planet Venus, Mid.Pers. Anahid “immaculate, unstained,” goddess of pure waters and fertility, from Av. arədvi-sûra-anâhita, from arədvi- “increasing, rising,” + sûra- “strong, powerful” (Skt. śūra- “valient, courageous”) + anâhita “unstained,” from an- negation prefix + âhita “spotted.”