An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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.

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.

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.

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.

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.

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 lé, all meaning "flood."

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.

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.

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.

Same as catalog position and → mean catalog place.

→ catalog; → place.

Same as catalog place and → mean catalog place.

→ catalog; → position.

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.

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.

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.

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.

A standard → syllogism that consists of three → categorical propositions in which there are three terms, and each term appears exactly twice. The three terms in a standard categorical syllogism are the → major term, → mino term, and → middle term.

→ categorical; → syllogism.

To place in a → category or class.

→ category; → -ize.

1) A group of things that are similar in some way.
2a) Philo.: In Aristotelian logic, any of the ten different ways (substance, quantity, quality, relation, place, time, position, possession, doing, and undergoing) in which the subject of a proposition may relate to its predicate. For example, the proposition "All men are mortal" belongs to the Category of Quality since it tells us what "all men" are like, namely mortal.
2b) Philo.: In Kant's system, any of the twelve (four groups of three each) pure concepts of the understanding that constitute necessary conditions of experience and correspond with the classes of judgements treated in formal logic. According to Kant, the categories are results of the mind's activity, and are distinguished from sensation. The categories have, furthermore, like space and time relations, a peculiar universality. They are, in other words, a priori.
3) Math.: An entity consisting of a class of objects and a class of → morphisms between those objects that satisfy certain properties.

M.Fr. catégorie, from L.L. categoria, from Gk. kategoria, from kategorein "to speak against; to accuse, assert, predicate," from kata "down, against, back," → cata-, + agorein "to speak before public assembly," from agora "marketplace, public square" (from ageirein "to gather"); cognate with L. grex, gregis "herd, troop, crowd;" Skt. gramah- "heap, crowd, community;" Old Icelandic kremja "to squeeze;" O.E. crammian "to cram;" Latvian  gùrste "bundle of flask;" Polish garnac "to gather;" Russ. gorst' "cupped hand;" cf. Pers. gor-, gal-, etc., as below; PIE base *ger- "to gather."

Katâgor, from katâ-, → cata-, + gor- "to gather," ultimately from PIE *ger-, as above. We put forward that the following Iranian words derive from the above PIE base *ger- "to gather":
goruh "crowd, troop, band;"
gallé (conversion of r to l) "herd, flock;"
jarra (Laki) "group; stick bundle;"
gerd in gerd âvardan "to collect, bring together" probably not related to gerd "round, circular;"
xalam (štiyâni) "herd, flock;"
xelima (Qâyeni) "herd;"
korand, korang "a ring made by hunters or troops;"
korka (Laki) "bundle of harvested ears of wheat;"
gola, golé "bundle of hair; bunch"
gola-gâh "place of gathering;"
gurâb "market place in a village, agora;"
There are dozens of villages all-over Iran named Gorâb, Gurâb, Gela, Gola, Gala and their combinations with other words (e.g. Galadeh, Galazan, Galavand) that probably refer to places of gathering.
One can also mention village names such as Agora, Gore, Gere(kalâ), Garaku, Oger, and so on in Mâzandarân;
Khotanese (prefixed ham-) gris "to assemble."

A theory that deals with the concept of → category and generalizes the → set theory.

→ category; → theory.

A negatively charged electrode that is the source of electrons in an electrical device.

Gk. kathodos "descent, a way down," from kata- "down" + hodos "way, path."