An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1335
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.


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.

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)

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.

  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.


Fr.: cataclysme   

1) A devastating flood; deluge.
2) Any violent upheaval that brings about great changes or causes great demolition. See also: → catastrophe.

From Fr. cataclysme, from L. cataclysmos "deluge," from Gk. kataklysmos, from kataklyzein "to inundate," from kata "down" + klyzein "to wash."

Gatlur "great flood," from gat "great, large, big" [Mo'in, Dehxodâ] + lur "flood" [Mo'in, Dehxodâ], cf. Gk. louein "to wash," L. luere "to wash," Bret. laouer "trough," PIE *lou- "to wash." Variants of lur in Pers. dialects are: Lori, Kordi laf, lafow, lafaw, Tabari , all meaning "flood."


Fr.: cataclysmique   

1) Of, pertaining to, or resulting from a → cataclysm.
2) Having the effect of, or of the nature of, a cataclysm. → cataclysmic variable.

cataclysm; → -ic.

cataclysmic variable
  ورتنده‌ی ِ گتلوری   
vartande-ye gatluri

Fr.: variable cataclysmique   

A → variable star that shows a sudden and dramatic change in brightness, including → flare stars, → novae, and some types of → symbiotic stars. They are believed to be very → close binary systems consisting of an → accreting → white dwarf  → primary and an evolved → late-type secondary star that has filled its → Roche lobe. For systems with an → accretion disk, it is believed that a thermal instability is the cause of repetitive outbursts observed in cataclysmic variables called → dwarf novae.

cataclysmic; → variable.

kâtâlog (#)

Fr.: catalogue   

A list or record of items systematically arranged with descriptive details. → Index Catalogue; → Messier catalog; → New General Catalogue.

M.E. cathaloge, cateloge, from M.Fr. catalogue, from L.L. catalogus, from Gk. katalogos "a list, register," from kata "down, completely" + legein "to say, count," → -logy.

Kâtâlog, loan from Fr., as above.

catalog place
  جای ِ کاتالوگی   
jâ-ye kâtâlogi

Fr.: position catalogue   

Same as catalog position and → mean catalog place.

catalog; → place.

catalog position
  نهش ِ کاتالوگی   
neheš-e kâtâlogi

Fr.: position catalogue   

Same as catalog place and → mean catalog place.

catalog; → position.


Fr.: catastrophe   

A great, often sudden calamity; a complete failure; a sudden violent change in the earth's surface. → cataclysm.

From Gk. katastrophe "an overturning, ruin," from katastrephein "to overturn, ruin" from kata "down" + strephein "to turn."

Negunzâr, from negun "overturned, inverted" + -zâr suffix denoting profusion, abundance, as in kârzâr "a field of battle; combat" šurezâr "unfertile, salty ground; nitrous earth," xoškzâr "arid land," and so forth.


Fr.: catastrophisme   

The doctrine that certain vast geological changes in the Earth's history were caused by sudden, short-lived, violent events rather than gradual evolutionary processes. Catastrophism explains the differences in → fossil forms encountered in successive → stratigraphic levels. This doctrine is associated with the French naturalist Baron Georges Cuvier (1769-1832). Catastrohism is contrasted to the → uniformitarianism.

catastrophe; → -ism.

  کتاگری، کتاگریک   
katâgori, katâgorik

Fr.: catégorique   

1) Unambiguously explicit and direct, without exceptions or conditions.
2) Relating to or included in a → category.
3) Logic: Of a → proposition (→ syllogism), consisting of a → subject and a → predicate, each of which denotes a class, and having one of the → Aristotelian forms.

category; → -ic; → -al.

categorical proposition
  گزاره‌ی ِ کتاگریک   
gozâre-ye katâgorik

Fr.: proposition catégorique   

In a → syllogism, a → proposition or statement that deals with inclusion or exclusion of members of → subject classes in → predicate classes. Categorical propositions are of four basic forms, see → Aristotelian form.

categorical; → proposition.

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