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: 13070 Search : far
Carrington rotation
  چرخش ِ کرینگتون   
carxeš-e Carrington

Fr.: rotation de Carrington   

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.

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

Cartesian
  دکارتی   
Descarti

Fr.: cartésien   

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.

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

Cartesian coordinates
  هم‌آراهای ِ دکارتی   
hamârâhâ-ye Dekârti

Fr.: coordonnées cartésiennes   

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.

Cartesian; → coordinate.

Cartesian vortex theory
  نگره‌ی ِ گردشار ِ دکارت   
negare-ye gerdšâr-e Descartes

Fr.: théorie des vortex de Descartes   

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.

Cartesian; → vortex; → theory.

Cartwheel Galaxy
  کهکشان ِ چرخ ِ ارابه   
kahkašân-e carx-e arrâbé

Fr.: galaxie de la roue de charette   

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.

Cartwheel, from cart from O.N. kartr; → wheel; → galaxy.

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."

cascade
  آبشار، پی‌شار   
âbšâr (#), peyšâr

Fr.: cascade   

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

From Fr., from It. cascata "waterfall," from cascare "to fall," from V.L. *casicare, from L. casum, p.p. of cadere "to fall," → case.

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."

cascade error
  ایرنگ ِ پی‌شاری، ~ آبشاری   
irang-e peyšâri, ~ âbšâri

Fr.: erreur en cascade   

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

cascade; → error.

cascade shower
  رگبار ِ پی‌شاری، ~ آبشاری   
ragbâr-e peyšâri, ~ âbšâri

Fr.: gerbe   

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

cascade; → shower.

cascade transition
  گذرش ِ پی‌شاری   
gozareš-e peyšâri

Fr.: transition en cascade   

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

cascade; → transition.

case
  کاته   
kâté

Fr.: cas   

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.

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.

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."

Casimir effect
  اُسکر ِ کازیمیر   
oskar-e Casimir

Fr.: effet Casimir   

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.

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

Cassegrain focus
  کانون ِ کسگرن   
kânun-e Cassegrain (#)

Fr.: foyer Cassegrain   

The main focus in → Cassegrain telescope.

Cassegrain telescope; → focus.

Cassegrain telescope
  دوربین ِ کسگرن، تلسکوپ ~   
durbin Cassegrain, teleskop-e ~ (#)

Fr.: Télecope Cassegrain   

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.

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

Cassini division
  شکاف ِ کاسینی   
šekâf-e Cassini (#)

Fr.: division de Cassini   

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

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

Cassini state
  استات ِ کاسینی   
estât-e Cassini

Fr.: état de Cassini   

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

Cassini's law; → state.

Cassini's law
  قانون ِ کاسینی   
qânun-e Cassini

Fr.: loi de Cassini   

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).

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.

Cassini-Huygens
  کاسینی-هویگنس   
Cassini-Huygens

Fr.: Cassini-Huygens   

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.

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.

Cassiopeia
  کاسیوپه   
Kâsiopé (#)

Fr.: Cassiopée   

A prominent circumpolar → constellation in the northern sky. Its brightest stars form a distinctive, turning W shape. Abbreviation Cas, genitive form Cassiopeiae.

L. Cassiopea, from Gk. Kassiepeia, Andromeda's mother and king Cepheus of Ethiopia's wife, who boasted about her beauty to the degree that she considered herself more beautiful than the sea-nymphs. The consequences were awful for her daughter → Andromeda.

Castor (α Geminorum)
  کاستور   
Kâstor

Fr.: Castor   

The second brightest star in the → constellation  → Gemini. This star has the identifier "alpha," but it is fainter than β Geminorum (→ Pollux). Castor was known as a main sequence, blue star of magnitude 1.98 and → spectral type A1. However, it is actually a → gravitationally bound family of six stars. The two brightest of the six, Castor A and Castor B, revolve around one another over a period of about 445 years. Castor A, the brighter of the two, is magnitude 1.9, while its companion is 3.0. Castor A is of spectral type A1 V and Castor B is Am. They are hotter than the Sun and about three times more massive, and lie 51 → light-years from Earth. Castor A and B are orbited by a third star called Castor C. It's a 9th magnitude → red dwarf (dMe1) and lies about one arc minute to the south. Castor C is about 1,000 → astronomical units from the bright pair and takes 14,000 years to orbit around them. Each of the three is a → spectroscopic binary making Castor a → sextuplet. Castor C is a → binary star of red dwarf stars a little more than half the size of the Sun. They revolve around one another evry 19 hours. The companions of Castor A and B are also smaller dwarf stars.

In Gk. mythology, Castor and → Pollux were twin heroes called the Dioscuri. Castor was the son of Leda and Tyndareus, Pollux the son of Leda and Zeus. They were great warriors and were noted for their devotion to each other. After Castor was killed by Lynceus, Pollux implored Zeus to allow his brother to share his immortality with him. Zeus created the constellation Gemini in their honor.

cata-
  کتا-، کاتا-، کات-، کت-   
katâ-, kâtâ-, kât-, kat-

Fr.: cata-   

A prefix meaning "down," also "against; back; by, about; with, along," occurring originally  in loanwords from Greek; variants cat- and cath-, as in catalog, cataclysm, cataract, cathode, catastrophe, etc.

From Gk. kata-, before vowels kat-, from kata "down from, down to."

Katâ-, kâtâ-, kât-, kat-, loan from Gk., as above.

<< < -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 aut axi Baa bal Bal bar bar bea beh 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 CGS cha cha che che chr cir cir cis 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 cov cre cri cro cry cur cut Cyg DA dar dat de deb dec dec ded def def dei dem den dep des det dev dia dif dif dig Dio Dir dis dis dis dis dis dis div dom dou dow dri dur dus dyn dyn ear eav ecl Edd eff Ein Ekm ele ele ele ele ell emb emi enc ene ent eph equ equ equ eru eth eup eve EX exc exe exi exo exp ext ext ext fab fai far Fec fem fer fie fin fir fis fla flo flu foc for for Fou fra fre fre fro fun G r Gal gal gam gas Gau gel gen geo geo geo Gho gla goa gra gra gra gra gre Gre gro gyr had hal har har HD Hea Hel hel Her her hid hig hip hol hor hos hov Hub Hun hyd hyd hyd hyp IC ide ill ima imp imp inc inc ind ind inf inf inf inf inj InS ins int int int int int int int int int inv ion iro ise iso iso ite jet Jou Jup kap Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea med men mer Mes met met mic Mic Mie Mil min mis mJy mod mol mon moo mot mul mul mut nad nas nat neb neg net neu New New nig Noe non non non Nor nov nuc nul num OB obl obs occ Ock off Ohm on- ope opi opt opt orb orb ord Ori ort osm out ove ozo pal pan par par par par pat pec pen per per per per per Pfu pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua qui rad rad rad rad rad rad rai ran Ras Ray rea rec rec rec red red ref reg reg rel rel rel rep res res res res Reu rhe Rie rig ris Roe Ros rot Rud ryd Sag sam sat sca sca Sch sci Sea sec sec see sel sem sen ser Sey Sha she sho sid sig sim sim sin ske sle smo Sob sof sol sol sol sol sou Sou spa Sp 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 ver vin vir vis Vog von wal wat wav wax wea wei Whi wil win WN7 wor X-r Yar You zer zod > >>