An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13046 Search : far
comet designation
  نامگزینی ِ دنباله‌دار   
nâmgozini-ye donbâledâr

Fr.: désignation des comètes   

A → nomenclature system for naming → comets. In early 1995, a new comet designation system was established by the → International Astronomical Union. The main rules are as follows:
a) If the comet is a newly discovered one, it first gets a provisional name, which closely matches the → asteroid designation system. For example, the first comet discovered in the first half of 1998 January is designated 1998 A1, the second 1998 A2, etc.
b) The name of the person(s) who discovered the comet may be added to this designation (limited, however, to three names). For example, comet → Hale-Bopp (C/1995 O1) has its full name as Hale-Bopp C/1995 O1, whereas its designation is C/1998 O1. If several people are involved with a discovery at an observatory, the comet may be named after the observatory instead of the individuals.
c) → Long-period comets and one-apparition → periodic comets receive only a provisional designation.
d) A → short-period comet would get the P/designation until it is recovered in a second → apparition. At this point, the P/Year designation would be replaced with a number followed immediately by an upper case P, and a slash followed by the name of the discoverer(s). The number here is one more than the number of known periodic comets that have reappeared. For example, the comet Hug-Bell (P/1999 X1) was given the full name 178P/Hug-Bell after it reappeared in 2007. Previously, 177 periodic comets had got assigned numbers.
e) Long-period comets are indicated by the prefix C.
f) If the comet is destroyed, or if it fails to appear after several apparitions, it would be prefixed D/ (→ defunct comet) followed by the year of its discovery. For example, → Comet Shoemaker-Levy 9 has been assigned D/1993 F2 since it was discovered in the second half of March in 1993 and was destroyed when it crashed into Jupiter in 1994.
g) Comets that lack sufficient position measurements for an orbital determination are given the designation of X/ followed by the year of their discovery and the appropriate letter and number code.
h) When a → comet nucleus nucleus splits, each fragment is given the comet designation followed by A, B, C, etc (for fragments).

comet; → designation.

comet family
  خانواده‌ی ِ دنباله داران   
xânevâde-ye donbâledârân (#)

Fr.: famille de comètes   

A group of comets with similar orbital characteristics. They result from perturbations by planets which change the diverse original orbits of the comets into those they now occupy.

comet; → family.

Comet Hale-Bopp (C/1995 O1)
  دنباله‌دار ِ هیل-بوپ، دمدار ِ ~   
donbâledâr-e Hale-Bopp, domdâr-e ~ (#)

Fr.: comète Hale-Bopp   

One of the brightest comets seen in the twentieth century, even though it came no closer to Earth than 1.32 AU (on 22 March 1997). It was visible to the naked eye for many months. The → nucleus of Hale-Bopp was estimated to be about 30 to 40 km across. Hale-Bopp has an orbital period of 2,380 years and is predicted to be seen again in AD 4377.

Discovered independently by American amateur astronomers Alan Hale and Thomas Bopp on July 22, 1995; → comet.

Comet Hyakutake (C/1996 B2)
  دنباله‌دار ِ هیاکوتاکه   
donbladâr-e Hyakutake

Fr.: comète Hyakutake   

A → long-period comet found in January 1996, which became the brightest comet since → Comet West in 1976. It was a bright naked-eye object and remained so in March, April, and May of 1996. At closest approach to Earth on March 25, is was only 0.10 AU away, displaying a long tail of up to 100 degrees. Small fragments were observed to break off the main nucleus. Hyakutake was the first comet from which X-ray emission was detected.

comet; Named after the Japanese amateur astronomer Yuuji Hyakutake (1951-2002), who discovered this comet in the morning of January 30, 1996.

comet nucleus
  هسته‌ی ِ دنباله‌دار   
haste-ye donbâledâr (#)

Fr.: noyau de comète   

The solid, centrally located part of a → comet. The nucleus is a mass of dust and frozen gases. When heated by the → Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the → coma, which is later swept into an elongated tail. Reliable measurements of cometary nuclei indicate sizes from a few km to 10 or 20 km. The nucleus of → Comet Hale-Bopp is one of the largest (perhaps 40 km). The composition of the nucleus is determined by measuring the composition of the coma (except for 67P/Churyumov-Gerasimenko). The dominant → volatile is → water, followed by → carbon dioxide (CO2), → carbon monoxide (CO), → formaldehyde (H2CO), → methanol (CH3OH), → methane (CH4) at a few percent level (with respect to water) and many other molecules at a lower level.

comet; → nucleus.

Comet Shoemaker-Levy 9
  دنباله‌دار ِ شومیکر-له‌وی   
donbâledâr-e Shoemaker-Levy 9

Fr.: comète Shoemaker-Levy 9   

A comet, formally designated D/1993 F2, whose shattered nucleus crashed into the planet → Jupiter over the period of July 16-22, 1994, several months after its discovery. The collision produced scars that were visible from Earth even in small telescopes. The cataclysmic event was the first collision between two → solar system bodies ever observed. The comet had been discovered on March 24, 1993, from photographs taken using the 0.46 m → Schmidt telescope at → Palomar Observatory. The appearance of the comet was reported as "most unusual": the object appeared as a "dense linear bar'' with a "fainter, wispy tail.'' The comet's brightness was reported as about magnitude 14, more than a thousand times too faint to be seen with the naked eye. Later observations revealed that the "bar'' was made up of as many as 21 pieces "strung out like pearls on a string,'' according to one researcher. Orbit calculations show that on July 7, 1992, the comet had passed only 25,000 km above Jupiter. The differential pull of the planet's enormous → gravitational force on the near and far sides of the comet fragmented it into the 21 or more pieces with sizes estimated at up to 2 km and an enormous amount of smaller debris. The comet had been in a rapidly changing orbit around Jupiter for some time before this, probably for at least several decades.

comet; Named after the husband and wife scientific team of American Carolyn S. (1929-) and Eugene M. Shoemaker (1928-1997) and Canadian amateur astronomer David H. Levy (1948-)

Comet West (C/1975 V1)
  دنباله‌دار ِ وست، دمدار ِ ~   
donbâledâr-e West, domdâr-e ~

Fr.: comète West   

A spectacular comet that at its closest approach to Earth reached a brightness of -1 magnitude. It was so bright that could be seen even at sunrise. The comet reached → perihelion on 1976 Feb. 25 at 0.20 A.U. and had a fan-shaped tail of dimensions 25° x 25° x 15° on the sky. A few days after perihelion, the nucleus split in four fragments. The → carbon monoxide (CO) molecule in comets was first detected in West. The comet's orbit has a period of about 500,000 years. Formerly designated 1976 VI.

After the Danish astronomer Richard M. West (1941-), who worked at the → European Southern Observatory (ESO); → comet.

cometary
  دنباله‌دار؛ گیسوار   
donbâledâr; gisvâr

Fr.: cométaire   

Of or relating to or resembling a → comet.

comet; → -ary.

cometary activity
  ژیرندگی ِ دنباله‌دار   
žirandegi-ye donbâledâr

Fr.: activité cométaire   

The appearance of → gas and → dust features from the rocky-icy nucleus of a comet when approaching the Sun (→ cometary atmosphere, → cometary tail). The → sublimation of → water can explain cometary activity at distances from the Sun up to about 4 → astronomical units. At larger distances, the average temperature of the → comet nucleus' surface is less than 140 K, too low for efficient sublimation of water → ice. However, there are many examples of cometary activity at larger distances. This can probably be due to the sublimation of more → volatile → chemical species. Indeed, radio spectroscopic observations of comets at large distances have revealed an important → outgassing of → carbon monoxide (CO), which can sublimate at temperatures as low as 25 K.

cometary; → activity.

cometary atmosphere
  جو ِ دنباله‌دار، هواسپهر ِ ~   
javv-e donbâledâr, havâsepehr-e ~

Fr.: atmosphère de comète   

The envelope of → gas and → dust around a → comet nucleus, also known as → coma. As the comet approaches the → Sun, the frozen materials → sublimate and give rise to an expanding atmosphere. The atmosphere is composed of dust, → molecules, → radicals, and molecular → ions released from the inner coma with velocities ~ 0.5 to 1 km s-1, well above the → escape velocity for the nucleus. The → chemical species observed in cometary spectra can be divided into several categories: (i) atoms and molecules related to → water (H, O, OH, OH+, H2O, H2O+), (ii) carbon and related molecules (C, C+, CO, CO+, CO2+, C2, CH, CH+, HCO, H2CO), (iii) → nitrogen and related molecules (CN, CN+, HCN, CH3CN, NH, NH2, N2+, NH3, NH4), (iv) → sulphur and related molecules (S, CS, S2, H2S+), (v) → metals (Na, K, Ca, Co, Cr, Cu, V, Fe, Mn, Ni). For a typical average comet the neutral atmosphere is first seen when the heliocentric distance is d ≤ 3 → astronomical units.

cometary; → atmosphere.

cometary globule
  گویچه‌ی ِ گیسوار   
guyce-ye gisvâr

Fr.: globule cométaire   

A relatively small cloud of → dust and → gas in the → interstellar medium shaped like a comet with a bright-rimmed head. Cometary globules are situated near young → massive stars with a strong → stellar wind. The wind ionizes gases on the side facing the → O stars and sweep away the low-density gas toward the tail. Cometary globules are believed to be → molecular cloud condensations, which are so dense that they are not disrupted when an → H II region expands into the molecular cloud surrounding it. The → Rosette nebula is a good example of an H II region which shows an abundance of cometary globules.

comet; → globule.

cometary nucleus
  هسته‌ی ِ دنباله‌دار   
haste-ye donbâledâr (#)

Fr.: noyau cométaire   

comet nucleus.

cometary; → nucleus.

cometary orbit
  مدار ِ دنباله‌دار   
madâr-e donbâledâr

Fr.: orbite de comète   

The → path followed by a → comet in the → solar system around the → Sun. Most cometary orbits appear to be → elliptical, or in some cases → parabolic. The orbits of → short-period comets are elliptical, carrying them out to a region lying from → Jupiter to beyond the orbit of → Neptune. Those of → long-period comets are very elliptical. The orbits may be strongly influenced if they pass near the Jovian planets, particularly Jupiter itself. The cometary orbits are also influenced to some degree by gases shooting out of comets, so their orbits are primarily but not completely determined by gravity. Newton (1644-1727) was the first to compute a cometary orbit. He found that the comet of 1680 was following a parabolic orbit around the Sun. Edmond Halley (1656-1742), following the methods of Newton, computed the → orbital elements of 24 comets. He realized that the comets of 1531, 1607 and 1682 had very similar elements and postulated that they were in fact the same object, orbiting an elongated ellipse. He predicted the next return to occur in 1758 or early 1759. The return of what is now called Halley's comet was observed after his death, This first observation of a "predicted" comet is manifestly one of the major successes of → celestial mechanics.

cometary; → orbit.

cometary tail
  دم ِ دنباله‌دار   
dome- donbâledâr

Fr.: queue de comète   

A formation of → gas and/or → dust that streams away from the → coma of many comets under the influence of the Sun's → radiation pressure and the → solar wind. See also: → dust tail, → gas tail, → ion tail, → plasma tail, → sodium tail, → Type I tail, → Type II tail, → antitail.

cometary; → tail.

commensurate
  هم مسا   
hammasâ

Fr.: commensurable   

(adj.) Of the same size, extent, or duration as another; proportionate.

L.L. commensuratus, from → com- "together, with" + mensuratus, p.p. of mensurare "to measure," from menusra "measure."

Hammasâ, from ham- "together," → com- + masâ "size, greatness," from Mid.Pers. masây, masâk "size," Av. masah- "size, greatness, length," maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest," cf. Skt. mah-, mahant-, Gk. megas, L. magnus; PIE *meg- "great."

commensurate orbits
  مدارها‌ی ِ هم مسا   
madârhâ-ye hammasâ

Fr.: orbites commensurables   

Of two bodies orbiting around a common barycenter, when the orbital period of one is an exact fraction, for example one-half or two-thirds, of the other.

commensurate; → orbit.

comment
  ۱) هامت؛ ۲) هامتیدن   
1) hâmat; 2) hâmatidan

Fr.: commentaire   

1a) A remark, observation, or criticism (Dictionary.com).
1b) A note in explanation, expansion, or criticism of a passage in a book, article, or the like; annotation (Dictionary.com).
2) To make remarks, observations, or criticisms (Dictionary.com).

M.E. coment, from O.Fr. coment "commentary;" L.L. commentum "comment, interpretation," in classical L. "invention, fiction," from comminisci "to contrive, devise," from → com-, intensive prefix + base of meminisse "to remember," related to mens, → mind.

Hâmat, from hâ-, intensive prefix, variant of ham-, → com-, + mat- "think; thought," from Av. mat- matay- "to think," humat- "good thought;" cf. Skt. matāy-.

commentary
  هامتگان   
hâmatgân

Fr.: commentaire   

1) A series of comments, explanations, or annotations (Dictionary.com).
2) An explanatory essay or treatise (Dictionary.com).

From M.E. commentaries (plural), from L. commentarium "notebook," noun use of neuter of commentarius, from comment(um), → comment, + -arium, → -ary.

Hâmatgân, from hâmat, → comment, + gân suffix forming plural entities, from Mid.Pers. -gânag, -gâna.

commentate
  هامتیدن   
hâmatidan

Fr.: commenter   

To deliver, to write a → commentary on.

Verb from → comment.

commentator
  هامتنده   
hâmatandé

Fr.: commentateur   

1) A person who makes commentaries.
2) A person who discusses news, sports events, weather, or the like, as on television or radio.

Agent noun from → commentate.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara arc Ari arr Asi ass ast ast asy atm ato att aut ave axi Bab bal ban bar bar bea Bel Bes bia Big bin bin bip Bla bla bli blu Boh Bon bos Bou bra bri bro bur cal cal can Cap car Car cat Cau cea Cen cen cha Cha cha che chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com com con con con con con con con con con con con coo cop Cor CoR cor cos cos Cou cou CP- cre cri cro cub cur cya Cyg dan dar dau de- deb dec dec dee def deg del den den dep des deu dew dia dif dif dih dip dir dis dis dis dis dis diu doc dop dou DQ dry dus dwa dyn Dys Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext eye fac fal Far fed Fer fer fie fin fir fit fla flo flu fol for for Fou fra fre Fre fro fuz gai Gal Gal gam gas Gau gen gen geo geo geo gia glo gol gra gra gra gra gre gri gui H I hai Ham har Hau hea hec hel hel her HES hie hig his hom hor hot Hub Hul Huy hyd hyd hyl hyp ice ide ima imm imp imp inc ind ind ine inf inf inf inh inn ins ins int int int int int int int int inv ion ion Irr iso iso iso Jal JHK Jul jur Kel Kep kin kne L d Lag lam Lap lar lat law Lea len lep lib lig lin lin lin liq lit loc log lon Los low lum lun Lut Lyr mac mag mag mag mag mag maj man Mar mas mas mat Max mea mec mel Mer Mes met met met mic mid Mil min mir mix mod mod mol mon mor mov mul muo mys nan nat Nav nec nep neu new New NGC Noa nom non non nor not nuc nuc num nyc obj obs obs oce odd OH Omi Oor ope opt opt opt orb ord Ori ort osc out ove oxi pai pan par Par Par par pas pea Pen per per per per Per per pha phl pho pho pho phy Pip Pla pla PLA pla ple plu pol pol pol pol pop pos pos pot Pra pre pre pre pre pri pri pro pro pro pro pro pro pro pse pul pur qua qua qua qua qui rad rad rad rad rad rad raf ran rar ray rea rea rec rec red red ref ref reg rel rel rel rep res res res res ret rev ric rig rin roc ROS rot Rox rus Sad sal sat sca sca Sch sci scy sec sec see sel sem sen Ser sex Sha she sho sid sig sil sim sin siz sle SMA SNR Sof sol sol sol sol sou Sou spa Sp spe spe spe sph spi Spi spr sta sta sta sta sta ste ste ste sto str str Sty sub sub suc sun sup sup sup sup sur Swa syn syn tac tas tel tem ter tes the the the the Tho thr tid tim Tit top tot tra tra TRA tra tre tri tri tru tum tur TY Typ ult una und uni uni uno upp urg UX Van var veg vel ver vib vio vir vis Voi vow wan wat wav WC wea wel whi Wil wir WNh wor X-r yel ytt zer zon > >>