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

An elongated → asteroid with dimensions of about 20 × 12 × 11 km. Gaspra is classified as an → S-type asteroid and is likely composed of metal-rich silicates and perhaps blocks of pure metal. It is a member of the → Flora family. It has a → rotation period of 7.04 hours. On October 29, 1991, the → Galileo spacecraft came within 1,600 km of Gaspra. They passed each other at 8 km/s. This was the first time that a spacecraft made a → flyby of an asteroid. Gaspra was discovered by Grigoriy N. Neujamin, Ukrainian astronomer, in 1916.

Named by its discoverer for a resort on the Crimean peninsula that was visited by contemporaries such as Tolstoy and Gorky.

An area on the surface of the → Moon that appears darker and smoother than its surroundings, once thought to be seas, now known to be lava-flooded basins; plural maria.

L. mare "sea," plural form maria, because Galileo thought the dark featureless areas on the Moon were bodies of water.

Daryânemâ literally "looking like a sea," from daryâ "sea" (Mid.Pers. daryâp variant zrah; O.Pers. drayah-; Av. zrayah- "sea;" cf. Skt. jráyas- "expanse, space, flat surface") + nemâ "looking, showing," present stem of nemudan "to show, display" (Mid.Pers. nimūdan, nimây- "to show," from O.Pers./Av. ni- "down; into," → ni-, + māy- "to measure," → display.

1) Logic: Relating to or involving inductive reasoning from particular facts or effects to a general principle (dictionary.com).
2) Logic: Derived from or requiring evidence for its validation or support; empirical; open to revision (dictionary.com). → a priori.

L., literally "from what comes after," from posterior "after, later, behind," comparative of posterus "coming after, subsequent," from post "after," → post-.

Afdom "the last," Dehxodâ: afdom "last, end;" Mid.Pers. abdom, apdom; from Proto-Ir. *apatama- superlative of *apa- "away from, from;" cf. Av. apəma- "the last, the most distant;" Skt. apamá-.

1) Logic: Relating to or involving deductive reasoning from a general principle to the expected facts or effects (dictionary.com).
2) Logic: Known to be true independently of or in advance of experience of the subject matter; requiring no evidence for its validation or support (dictionary.com). → a posteriori.

L., literally "from what comes first," from priori, ablative of prior "former, previous, first," → per-.

Partom "the first," Dehxodâ: fardom; Mid.Pers. fradom, fratom, pratom; O.Pers. fratama-; Av. fratəma- (Skt. prathama- "earliest, initial, first") superlative of fra- "before, forward, forth," cognate with Gk. and L. → pro-.

One of → Saturn's rings, lying beyond the → B ring at 122,170 km from the center of Saturn, with a width of 14,600 km.

→ ring.

A star whose spectrum shows strong hydrogen → Balmer lines accompanied by many faint to moderately strong metallic lines. In contrast to B and O stars, the lines of He I and He II are absent. Their surface temperature ranges from 7,500 to 10,000 K. The main metallic lines seen in A-type stars are those of Fe I and Fe II, Cr I and II, Ti I and II, and account for about two-thirds of all lines. Some famous examples of A star are: → Sirius; → Deneb, → Altair, and → Vega. Also known as A-type star.

A, letter of alphabet used in the → Harvard classification; → type; → star.

Prefix meaning "not."

From Gk. a-, an- "not," compare with O.Pers./Av. a-, an- "not, without," Skt. a-, an- "not," L. in-, a variant of PIE *ne- "not".

A-, an-, from O.Pers./Av. negation prefix appearing before consonants and vowels respectively. A couple of examples in Mod.Pers.: amordâd "immortality, name of the fifth month in the Iranian calendar," anušé; "fortunate, happy," anirani "non Iranian," âhu "vice, defect," âsoqdé "unburnt, half-burnt wood."
Bi- privative prefix, from Mid.Pers. abi-, O.Pers. *apaiy-, Av. apa-.
Nâ- negation prefix "not, no," Mid.Pers. ne, O.Pers. naiy, Av. na-, (particle of negation noit), Skt. na-, (ned), Gk. né- "not," L. ne-, in-, un-, PIE *ne-.

Same as → A star.

A, letter of alphabet used in the → Harvard classification; → type; → star.

→ 1I/'Oumuamua.

→ asteroid designation.

A → thought experiment conceived by Einstein (1879-1955) at the age of sixteen in the Swiss town of Aarau where he attended the Argovian cantonal school. If an → observer moved at the → speed of light, pursuing a → beam of light, would he → observe such a beam of light as a spatially oscillatory → electromagnetic field at rest? The answer came some ten years later from Einstein himself by his theory of → special relativity. Accordingly, the speed of light is constant for all observers and no observer can move at the light velocity.

Aarau, the Swiss town, the capital of the northern Swiss canton of Aargau; → paradox.

A → quadruple system of stars consisting of two close pairs, AB Dor A / AB Dor C and AB Dor Ba / AB Dor Bb, separated by about 9 arcseconds. The brightest star of the system, AB Dor A, is a → pre-main sequence star of → spectral type K1, with strong emission at all wavelengths, from radio to X-rays. The companion of this star, i.e. component C, lying 0.185 arcseconds apart, is a very low-mass star of 0.090 → solar masses with a spectral type M 5.5 (Boccaletti et al. 2008, A&A 482, 939 and references therein).

A, a, B, b, and C designating letters of alphabet; → Dorado.

"From the beginning," as opposed to in medias res "starting in the middle of the story." In physics and chemistry "from first principles;" → ab initio calculation.

L. "from the beginning," from ab "from," → ab- + initio, ablative of initium "a beginning, an entrance," from inire "to go into, begin," from in- "into, in" + ire "to go" (cf. Gk. ienai "to go," Skt. eti "goes," O.Pers. aitiy "goes," Av. aeiti "goes," Mod.Pers. âyad "comes," PIE *ei- "to go, to walk").

Hac bon, from Mid.Pers. hac "from" (O.Pers. hacā "from," Av. hacā "from, out of," cf. Skt. sácā "with," PIE base *sek^w- "to follow," Av. hac-, hax- "to follow," hacaiti "follows," Skt. sácate "accompanies, follows," Gk. hepesthai "to follow," L. sequi "to follow," Lith. seku "to follow") + bon "beginning, base, root" (Av. būna- "base, depth," cf. Skt. bundha-, budhná- "base, bottom," Pali bunda- "root of tree").

In physics and chemistry, a calculation that relies on basic and established laws without additional assumptions or special models. Experimental input in ab initio calculations is limited to the determination of values of fundamental physical constants.

→ ab initio; → calculation.

A → photometric system defined by reference to → monochromatic magnitudes in such a way that, when monochromatic → flux f_ν is measured in ergs sec^-1 cm^-2 Hz^-1, the magnitude will be: AB = -2.5 logf_ν - 48.60. The constant is set so that AB is equal to the V magnitude for a source with a flat → spectral energy distribution. The → zero point is defined by the flux of the star → Vega at 5546 Å. In this system, an object with constant flux per unit frequency interval has zero color.

→ magnitude; → system.

1) To leave completely and finally; forsake utterly; desert.
2) To give up; discontinue; withdraw from (Dictionary.com).

M.E. abando(u)nen, from M.Fr. abandoner, from O.Fr. abandoner from adverbial phrase à bandon "at will, at discretion," from à "at, to," → ad-, + bandon "power, jurisdiction," from L. bannum "proclamation."

Râcidan, related to Pers. parhêz, parhiz "to keep away from, abstain, avoid," gurêz, goriz "to flee, run away;" Av. raēc- "to leave, let;" → heritage.

The reciprocal of the → dispersive power of a substance. Also known as constringence.

→ Abbe sine condition; → number.

In → geometric optics, a condition for eliminating → spherical aberration and → coma in an → optical system. It is expressed by the relationship: sin u'/U' = sin u/U, where u and U are the angles, relative to the → optical axis, of any two rays as they leave the object, and u' and U' are the angles of the same rays where they reach the image plane. A system which satisfies the sine condition is called → aplanatic.

Named after Ernst Karl Abbe (1840-1905), a German physicist; → sine; → condition.

The → locus of the intersection of input and output → conjugate rays in an optical system satisfying the → Abbe sine condition.

→ Abbe sine condition; → sphere.

1) If a → power series → converges for some nonzero value x₀, then it converges absolutely for any value of x, for which |x| < |x₀|.
2) If a power series → diverges for some nonzero value x₀, then it diverges for any value of x, for which |x| > |x₀|.

Named after the Norwegian mathematician Niels Henrik Abel (1802-1829); → theorem.

A catalog of 4073 rich → galaxy clusters grouped by constellation and by catalog number. Published first in 1958, it contained the clusters visible from the northern hemisphere. A supplement for the southern hemisphere survey was published in 1988.

George O. Abell (1927-1983), American astronomer; → catalog.