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

The autocovariance function (ACF) is defined as the sequence of covariances of a stationary process.
A mathematical function that expresses the autocovariance of a series in terms of the interval of separation.

→ autocovariance; → function.

An electronic equipment used to automatically guide a telescope during long exposures.

Autoguider from → auto- "self" + guider, from O.Fr. guider "to guide, lead, conduct," from Germanic origin; akin to O.E. wltan "to look after" witan "to know," akin to O.H.G. wizzan "to know," L. videre "to see," Gk. eidenai "to know," idein "to see," Av. vaêd- "to know," Skt. veda "knowledge; finding."

Xodrâhbar from xod-, → auto + râhbar "guide," from râh "way" + bar, from bordan "to lead."

The act or process of guiding a telescope automatically.

→ autoguider.

Having a self-acting or self-regulating mechanism.

From Gk. automatos "self-acting," from → auto- + matos "willing," from PIE *men- "to think;" compare with Av./O.Pers. man- "to think."

Xodkâr from xod-, → auto-, + kâr "acting, actor," from kardan "to do, act."

A telescope developed to perform photometric observations automatically.

→ automatic; → photometric; → telescope.

An → isomorphism between an → object and itself.

→ auto-; → morphism.

1) Self-governing; independent; subject to its own laws only; having autonomy.
2) Pertaining to an autonomy, or a self-governing community.
3) Biology: Existing and functioning as an independent organism. Growing naturally or spontaneously, without cultivation (Dictionary.com).

Adjective from → autonomy.

1) Independence or freedom, as of the will or one's actions.
2) The condition of being autonomous; self-government or the right of self-government (Dictionary.com).

→ auto-; → -nomy.

The season of the year between summer and winter; it begins in the northern hemisphere at the → autumnal equinox and ends at the → winter solstice.

O.Fr., from L. autumnus, a word probably of Etruscan origin.

Pâyiz, from Mid.Pers. pâdiz or pâtez, from Proto-Iranian *pâti-z(a)ya- "near winter," from pâti "near" + *z(a)ya- "winter," compare with Av. zyan- or zyam- "winter" (Skt. heman, Gk. xeimon, L. hiems).

→ autumnal equinox.

→ autumn; → equinox.

One of the two points where the → ecliptic crosses the → celestial equator. At the autumnal equinox the Sun appears to be moving across the equator from the northern celestial hemisphere to the southern celestial hemisphere. The instant of the event.

→ autumn; → -al; → equinox.

A number representing a group of quantities, obtained by adding each quantity of the group and dividing the total by the number of quantities. Same as → arithmetic mean.

From O.Fr. avarie "damage to ship," from It. avaria or maybe avere, O.Fr. aveir "property, goods," from L. habere "to have." Meaning shifted to "equal sharing of such loss by the interested parties."

Miyângin "the middle; middle-sized; the middle pearl in a string," from miyân, → middle, + -gin a suffix forming adjectives of possession.

Of a body traveling from A to B, the change of → velocity divided by the time interval: ā = (v₂ - v₁) / (t₂ - t₁).

→ average; → acceleration.

The ratio of the displacement (Δx) of a particle, as it moves from point A to point B, to the corresponding time interval: v = Δx/Δt.

→ average; → velocity.

The technique of looking slightly to the side of a faint object being studied while continuing to concentrate on the object. The technique helps bring out details which otherwise would be missed by looking directly at an object. The reason is that the portion of the eye's retina that best detects dim light (fovea) is located all around the edges rather than the center.

Averted p.p. from avert, from O.Fr. avertir, from L. avertere "to turn away," from → ab- "from, away" + vertere "to turn" (cognate with Pers. gardidan "to turn"); → vision.

Negâh, → vision; kaž "averted."

The number of units in one → mole of any → substance (defined as its → molecular weight in grams), equal to 6.022 140 857 × 10²³. The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance.

Named after Amedeo Avogadro (1776-1856), whose law allowed other physicists to calculate Avogadro's number; → number.

A statement according to which equal volumes of different gases contain an equal number of molecules under the same conditions of temperature and pressure.

After Amedeo Avogadro (1776-1856), Italian chemist and physicist, who advanced the hypothesis in 1811.

→ Avogadro constant.

Named after Amedeo Avogadro (1776-1856), whose law allowed other physicists to calculate Avogadro's number; → constant.

1) To keep away from; keep clear of; shun.
2) To prevent from happening (Dictionary.com). → abstain.

M.E. avoiden, from Anglo-French avoider "to clear out, withdraw (oneself)," from O.Fr. esvuidier "to empty out," from es- "out," → ex-, + vuidier "to be empty," from voide "empty, vast, waste," from L. vocivos "unoccupied, vacant," vacare "be empty," from PIE base *eue- "to leave, abandon, give out."

Tosnidan, from Baluci tôsênag "avoid," tusag "be quenched," tôsaq "quench;" related to Pers. tohi "empty, void;" Mid.Pers. tuhig "empty;" Parthian tôšênitan "to empty;" cf. Pashto taš; Ormuri tusk; Waxi töš, təš; Sariqoli tīs; Skt. tucchá-, tucchyá- "empty;" L. tesqua "deserts;" O.Slav tušti "empty;" Russ. tošcij "meager."

Able to be avoided or prevented.

→ avoid; → -ance.