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: 13048 Search : far
Cheops
  خءوپس   
Cheops

Fr.: Cheops   

The first mission, conducted by the → European Space Agency, dedicated to searching for → exoplanetary transits by performing ultra-high precision → photometry on bright stars already known to host planets. Launched on 18 December 2019, Cheops is a small spacecraft with a launch mass (including propellant) of approximately 280 kg. It has a single instrument: a high precision → photometer with a 300 mm effective aperture telescope and a single → charge-coupled device (CCD) → detector covering → visible to → near-infrared wavelengths. The mission's main science goals are to measure the bulk density of → super-Earths and Neptunes orbiting bright stars and provide suitable targets for future in-depth characterization studies of → exoplanets in these mass and size ranges.

CHEOPS, short for CHaracterising ExOPlanet Satellite.

Cherenkov radiation
  تابش ِ چرنکوف   
tâbeš-e Čerenkov (#)

rayonnement de Čerenkov   

Visible radiation emitted when → charged particles pass through a transparent medium faster than the speed of light in that medium.

Named after Pavel A. Čerenkov (1904-1990), Russian physicist, who discovered the phenomenon. He shared the Nobel prize 1958 in physics with Ilya Frank and Igor Tamm, who in 1937 gave the theoretical explanation for this radiation.

chi-square distribution
  واباژش ِ خی-دو   
vâbâžeš-e Xi-do

Fr.: loi du chi-deux   

A probability density function, denoted χ2, that gives the distribution of the sum of squares of k independent random variables, each being drawn from the normal distribution with zero mean and unit variance. The integer k is the number of degrees of freedom. The distribution has a positive skew; the skew is less with more degrees of freedom. As degrees of freedom increase, the chi-square distribution approaches a normal distribution. The most common application is chi-square tests for goodness of fit of an observed distribution to a theoretical one. If χ2 = 0 the agreement is perfect.

Chi Gk. letter of alphabet; → square; → distribution.

Vâbâžeš, → distribution; do, → two.

Chicxulub crater
  لاوک ِ چیکخولوب   
lâvak-e Cikxulub

Fr.: Cratère de Chicxulub   

A crater about 200 km in diameter on the northern coast of the Yucatan Peninsula, near the town of Chicxulub, Mexico. It is attributed to a 10 km wide → asteroid that hit the Earth about 65 million years ago (→ Chicxulub impactor). Ten years before the 1990 discovery of the Chicxulub crater, physicist Luis Alvarez and geologist Walter Alvarez proposed a theory to explain the formation of the crater. They noted increased concentrations of the element → iridium in 65-million-year-old clay. Iridium is rare on Earth, but it's more common in some objects from space, like → meteors and asteroids. According to the Alvarez theory, a massive asteroid had hit the Earth, blanketing the world in iridium. The collision caused fires, climate change and widespread extinctions, among which that of dinosaurs, who had lived for 180 million years.

Named after a twon in the Mexican state of Yucatan, which lies near the geographic center of the → crater.

Chicxulub impactor
  برخوردگر ِ چیکخولوب   
barxordgar-e Cikxulub

Fr.: impacteur de Chicxulub   

An object having an estimated mass between 1.0 × 1015 and 4.6 × 1017 kg, which struck the Earth at the → Cretaceous-Tertiary event about 65 million years ago. It was probably an → asteroid 10 km in diameter with a velocity of roughly 20 km per sec at an angle of just under 60°. The collision created the → Chicxulub crater. The event was responsible for eliminating approximately 70 percent of all species of animals at or very close to the boundary between the Cretaceous and Paleogene periods.

Chicxulub crater; → impactor.

child
  فرزند   
farzand (#)

Fr.: enfant   

1) A person between birth and puberty; a son or daughter; an offspring.
2) In → graph theory, the → vertex (node) below a given vertex connected by its → edge downward. In other words, in a rooted tree, a vertex v is a child of vertex w if v immediately succeeds w on the path from the root to v. Vertex v is a child of w if and only if w is the parent of v.

M.E.; O.E. cild "fetus, infant;" akin to Goth. kilthai "womb."

Farzand, from Mid.Pers. frazand "child;" Av. frazanti- "progeny, offspring," from fra- "forward, along," → pro-, + zan "to give birth;" → birth.

Chinese calendar
  گاهشمار ِ چینی   
gâhšomâr-e Cini

Fr.: calendrier chimois   

A → lunisolar calendar (Chinese: yīnyáng li), which is now mainly used for determining cultural festivals. It is based on astronomical observations of the Sun's annual apparent motion (→ ecliptic) and → lunar phases. The calendar starts at Chinese New Year and consists of 12 or 13 → lunar months. The ecliptic is divided into 24 sections (jiéqi) of 15° each. In general, Chinese New Year falls on the day of the second new Moon after the → winter solstice on approximately December 22. Since 12 months are about 11 days shorter than the → tropical year, a → leap month is inserted to keep the calendar in tune with the seasons. An ordinary → lunar year has 353-355 days while a → leap year has 383-385 days. Therefore, the → solstices and → equinoxes move 11 (or 10 or 12) days later. Each 13-month leap year is about 19 days too long, so the solstices and equinoxes jump 19 (or 18 or 20) days earlier. Each year is assigned a name consisting of two components within a 60-year cycle. The first component is a celestial stem. The second component is a terrestrial branch; it features the names of animals in a zodiac cycle consisting of 12 animals. Each of the two components is used sequentially. Therefore, the first year of the 60-year cycle becomes jia-zi, the second year is yi-chou, and so on. One starts from the beginning when the end of a component is reached. The 60th year is gui-hai. The current 60-year cycle started on 2 February 1984. The leap year must be inserted if there are 13 new moons from the start of the 11th month in the first year to the start of the 11th month in the second year. The beginnings of the Chinese calendar can be traced back to the 14th century BC. Legend has it that the Emperor Huang-di invented the calendar in 2637 BC. The calendar has been adopted by several southeast Asian cultures. The Chinese calendar has undergone several reforms, the last one in 1645. For more details, see, e.g., Helmer Aslaksen, The Mathematics of the Chinese calendar, e-paper.

Chinese adj. of China, from Pers. Cin [Chin], from Qin the first imperial dynasty of China (221 to 206 BC); → calendar.

chiral
  خیرال   
xirâl

Fr.: chiral   

The quality of an object that is not superimposable on its mirror image.

From Gk. cheir "hand;" from PIE *ghes- "hand."

Xirâl, loan from Gk., as above.

chirality
  خیرالی   
xirâli

Fr.: chiralité   

The geometric property of a rigid object that is → chiral.

chiral; → -ity.

Chiron
  خیرون   
Xeiron (#)

Fr.: Chiron   

An object, discovered in 1977, which was initially assumed to be an asteroid, but subsequent observations showed it to be a weak comet with a detectable coma. Its orbit, lying now between those of Saturn and Uranus, is unstable on time scales of a million years.

In Gk. mythology, Xειρων (Cheiron or Chiron) was the wisest of the Centaurs; he was not a drunkard like other Centaurs. Chiron was tutor to Jason and Heracles. He was the only immortal centaur.

chirp
  چیرپ   
cirp

Fr.: compression d'impulsion   

1) Telecommunications: A signal in which the wave frequency increases or decreases, linearly or exponentially, with time.
2) Astro: The theoretically predicted → gravitational wave arising from the interaction of two highly → compact objects. As the two objects spiral toward each other, due to orbital energy loss, the frequency and amplitude of the gravitational wave will increase continuously.

Chirp "a short, high-pitched sound, such as that made by certain birds or insects," from M.E. chirpen, of onomatopoeic origin.

Cirp loanword from E., as above.

Chladni pattern
  الگوی ِ کلادنی   
olgu-ye Chladni

Fr.: figure de Chladni   

A pattern formed by fine powder or salt placed on a vibrating surface. The figures display the positions of → nodes and → antinodes.

Named after Ernst Chladni (1756-1827), German physicist; → figure.

chlorate
  کلرات   
klorât (#)

Fr.: chlorate   

1) A negative ion, ClO3- derived from chloric acid.
2) Any salt of chloric acid.

From chlor-, → chlorine, + → -ate.

chloric acid
  اسید کلریک   
asid klorik (#)

Fr.: acide chlorique   

A colorless, strong acid HClO3, formed by the action of dilute sulfuric acid on barium chlorate.

From chlor-, → chlorine, + → -ic; → acid.

chlorine
  کلور   
klor (#)

Fr.: chlore   

A gaseous → chemical element of the halogen group, which is greenish yellow and poisonous; symbol Cl. → Atomic number 17; → atomic weight 35.453; → melting point -100.98°C; → boiling point -34.6°C. Chlorine is about two and one-half times as dense as air. It is used for water purification, in the making of bleaching powder. Its compounds occur as common → salt (sodium chloride), NaCl, in sea water and as rock salt. Chlorine is the first poison gas to be used in warfare (by German army, the Second Battle of Ypres, 1915). It has several → radioactive isotopes, in particular 36Cl with a half-life of 3 × 105 years. Chlorine was discovered by the Swedish pharmacist and chemist Carl-Wilhelm Scheele (1742-1786) in 1774. In 1810, the English chemist Humphry Davy (1778-1829) proved it was an element and gave it the name chlorine.

From Gk. chloros "light green, greenish yellow;" cognate with Pers. zard "yellow," zarr "gold;" E. → gold, → yellow.

chondrite
  کوندریت   
kondrit

Fr.: chondrite   

The most common type of → meteorites containing → chondrules. These → stony meteorites make up about 86% of all meteorites. An important feature of the chondrites is that, with the exception of a few highly → volatile elements, they have the same composition as the Sun.

Chondrite, from chondr-, from chondros "grain", + suffix → -ite.

chondrule
  کوندرول   
kondrul

Fr.: chondrule   

Millimeter-sized grains of → silicate sometimes found in large numbers in → chondrite meteorites. They are essentially glassy beads made by a violent but brief heating event that caused dust grains to form melt droplets. However, the cause of the heating remains unknown.

From Gk. chondr-, from chondros "grain," + diminutive suffix → -ule.

chough
  کلجیک   
kalajik

Fr.: crave à bec rouge   

A member of the → crow family with a red beak and legs.

M.E. choghe; akin to O.E. ceo, Du. kauw, Dan. kaa.

Kalajik, from Daštak Baxtiyâri dialect, related to kal, kalâq, → crow.

Christoffel symbol
  نماد ِ کریستوفل   
namâd-e Christoffel (#)

Fr.: symbole de Christoffel   

A abbreviated notation for various functions associated with quadratic differential forms. Each Christoffel symbol is essentially a triplet of three indices, i, j and k, where each index can assume values from 1 to 2 for the case of two variables, or from 1 to n in the case of a quadratic form in n variables. Christoffel symbols appear in many calculations in geometry where non-Cartesian coordinates are used. These symbols are fundamental in the study of tensor analysis.

Named after Elwin Bruno Christoffel (1829-1900), a German mathematician; → symbol.

chromatic
  رنگی، فامی   
rangi, fâmi

Fr.: chromatique   

Of or relating to color or color phenomena or sensations.

From L. chromaticus, from Gk. khromatikos "relating to color," from khroma, khromat- "color" + → -ic.

From rang, fâm, → chromo-, + -i adj. suffix.

<< < -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 ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu 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 con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp 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 phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>