An Etymological Dictionary of Astronomy and Astrophysics

A type of → achondrite meteorite composed mostly of the magnesium silicate mineral → enstatite (Mg₂Si₂O₆). The group is named for the small Aubres → meteorite that fell near Nyons, France, on Sep. 14, 1836. Outside Antarctica only about 10 aubrites are known, mostly the result of witnessed falls. Aubrites make up only 0.14% of all known meteorites in our terrestrial meteorite collection.

See also: From Fr. Aubres, a commune in the Drôme department in southeastern France; + → -ite.

An electron that is emitted when an electron from a higher → energy level falls into a → vacancy in an inner shell, according to the → Auger-Meitner effect.

The process usually occurs when the atom is bombarded with high energy electrons.

If the collision ejects an inner-shell electron, an electron from a higher level will quickly drop to this lower level to fill the vacancy.

Most of the time, the energy is released in the form of a photon.

But sometimes the energy is transferred to another electron, which is ejected from the atom.

See also: → Auger-Meitner effect; → electron.

The → emission of an → electron when an → atom transits to a less → excited state. More specifically, → ionization of an atom by a very energetic photon can bring about the ejection of an inner electron of the atom. Consequently, the atom becomes unstable and rapidly undergoes a → spontaneous transition. As a result, an outer electron moves inward and fills the → vacancy produced in the inner orbit. Energy conservation requires that this transition be accompanied by the emission of a photon or a peripheral electron. The latter is called the → Auger electron. Knowing the electron energy leads us to characterize the atom from which it was ejected. This effect is used, in the Auger spectroscopy, to analyze the surface compositions of materials.

See also: This effect was discovered in 1923 Lise Meitner (1878-1968) and in 1925 independently by Pierre Auger (1899-1993).

The Charioteer. A conspicuous northern constellation lying midway between → Perseus and → Ursa Major and in a region crossed by the → Milky Way. The brightest star is → Capella.
Auriga is the site of the Galactic → anticenter. Abbreviation: Aur; genitive form: Aurigae.

Etymology (EN): L. auriga “a charioteer, driver,” from aureæ “bridle of a horse” + agere “set in motion, drive, lead.”

Etymology (PE): Arrâberân “charioteer,” from arrâbé “chariot, cart”

• rân “driver,” from rândan “to drive.” Arrâbé probably from *arâba, from *râba, from *râda, compare with Av. ratha- “chariot,” akin to Skt. rathah “car, chariot,” L. rota “wheel,” rotare “revolve, roll,” Lith. ratas “wheel,” O.H.G. rad, Ger. Rad, Du. rad, O.Ir. roth; PIE *roto- “to run, to turn, to roll."
  Gardunerân “a charioteer,” from garduné “chariot, car,” from gardun “wheel; heaven,” from gardidan “to turn, revolve.”

A phenomenon consisting of luminous colorful arcs, rays, and streamers that appear in the Earth’s upper atmosphere during the night with the greatest frequency in the northern and southern polar magnetic zones. This → non-thermal radiation is caused by the emission of light from atoms excited by electrons accelerated along the planet’s magnetic field lines at the magnetic poles. Fluorescent emission from atomic oxygen at 5557 Å results in a greenish glow, and there is a weaker effect from the red line at 6300 Å. Blue and purple colors are emitted by atomic and molecular nitrogen.

Etymology (EN): L. Aurora, the Roman goddess of dawn, akin to Av. uš-, ušah- “dawn,” Skt. usas-, usah- “dawn,” Gk. eos “dawn,” Lith. ausra “dawn,” O.E. east “east,” PIE *ausus- “dawn,” from *aus- “to shine.”

Etymology (PE): Ušé, from Av. uš-, ušah-, as above.

The aurora in the Southern hemisphere, also called as Southern Lights.

See also: → aurora; → south.

The aurora in the Northern hemisphere, also called as Northern Lights.

See also: → aurora; → north.

Pertaining to the → aurora phenomenon.

See also: → aurora; → -al.

The → electromagnetic radiation emitted in planetary atmospheres involving the → aurora phenomenon.

See also: → auroral; → emission.

1. A prominent → forbidden line in the spectra of the aurora at wavelengths of 5577 and 6300 Å giving the aurora its characteristic green and red colors.
   Both are emitted by atomic oxygen, the former in its transition from the second lowest excited electronic state (¹S) to the lowest excited electronic state (¹D), the latter in its transition from the lowest excited electronic state (¹D) to the atomic ground state (³P).
   
2. A forbidden line emitted by interstellar ionized gas by several atomic species (O, O⁺, O⁺⁺, N⁺, S⁺⁺, etc.) corresponding to the transition from the state ¹S to ¹D. → forbidden line; → nebular line; → transauroral line.

See also: → auroral; → line.

A roughly circular band around either geomagnetic pole above which there is a maximum of auroral activity. It lies about 10 to 15° of geomagnetic latitude from the geomagnetic poles.

See also: → auroral; → zone.

1. To establish as genuine.
   

2. To prove beyond doubt the authorship or origin of (e.g. to authenticate a painting). → authentication.

Etymology (EN): From L.L. authenticus, from Gk. authentikos “original, primary, at first hand,” from authent(es) “one who does things himself,” from aut-, from autos “self, one’s own,” of unknown origin,

• -hentes “doer” + -ikos, → ics.

Etymology (PE): Râstin “genuine, authentic,” from râst “right, true; just, straight” (Mid.Pers. râst “true, straight, direct;” O.Pers. rāsta- “straight, true,” rās- “to be right, straight, true;” Av. rāz-
“to direct, put in line, set,” razan- “order;” cf. Skt. raj-
“to direct, stretch,” rjuyant- “walking straight;” Gk. orektos “stretched out;” L. regere “to lead straight, guide, rule,” p.p. rectus “right, straight;” Ger. recht; E. right; PIE base *reg- “move in a straight line,” hence, “to direct, rule”)

• -in adj. suffix.
  Šomârdan “to consider; to reckon, count, compute;” Mid.Pers. ôšmârtan, ôšmurtan “to reckon, calculate, enumerate, account for,” from Av. base (š)mar- “to have in mind, remember, recall,” pati-šmar- “to recall; to long for,” hišmar-, cf. Skt. smar- “to remember, become aware,” smarati “he remembers,” L. memor, memoria, Gk. mermera “care,” merimna “anxious thought, sorrow,” martyr “witness.”

Computers: The process by which a user’s identity is checked within the network to ensure that the user has access to the requested resources.

See also: Verbal noun of → authenticate.

1. The writer of a book, article, or other text. One who practices writing as a profession.
   

2. An originator or creator, as of a theory or plan.
   

3. Author God.

Etymology (EN): M.E. auctour, from O.Fr. autor, from L. auctor, “creator, enlarger, founder, master, leader,” literally “one who causes to grow,” from auctus, p.p. of augere “to increase,” from PIE root aug- “to increase”.

Etymology (PE): Dâtâr, from Mid.Pers. dâtâr/dâdâr “creator,” from Av. and O.Pers. dâtâr “creator,” from dâ- “to create, make, appoint,” Skt. dhatr “author, creator, preserver, bearer.”
The Mod.Pers. form of this word in classical literary works is dâdâr, used mainly as noun or adjective for “God, the creator.”

Of, relating to, or characterized by strict obedience to authority.

See also: From authorit(y), → authority, + suffix -arian.

1. The enforcement or advocacy of strict obedience to authority at the expense of personal freedom.
   

2. Lack of concern for the wishes or opinions of others (OxfordDictionaries.com).

See also: → authoritarian; → -ism.

1. Recognized or accepted as being true or reliable.
   

   2. Exercising or asserting authority; commanding.
      

   3. Possessing or supported by authority; official (Dictionary.com).

See also: From authorit(y), → authority, + suffix -ative.

1. The power to determine, adjudicate, or otherwise settle issues or disputes; jurisdiction; the right to control, command, or determine (Dictionary.com).
   

2. A person or body of persons in whom authority is vested, as a governmental agency (Dictionary.com).

Etymology (EN): → author; → -ity.

Etymology (PE): Dâtârgân, from dâtâr, → author, + -gân, on the model of xodâygân “a great lord.”

1. The act, fact, or occupation of writing.
   
2. Source or origin, as of a book or idea.

See also: → author.

Etymology (EN): Gk., from autos “self, one’s own,” of unknown origin.

Etymology (PE): Xod-, from xod “self,” Av. hva- “self, own.”

1. In radio astronomy, a process performed by an → autocorrelator.
   
2. In statistics, a linear relation between values of a random variable over time.
   
3. In electronics, a technique used to detect cyclic activity in a complex signal.

Etymology (EN): Autocorrelation, from → auto- “self” + → correlation.

Etymology (PE): Xod-hambâzâneš, from xod- “self” + hambâzâneš,
→ correlation.

A mathematical function that describes the correlation between two values of the same variable at different points in time.

See also: → autocorrelation; → function.

In radio astronomy, a spectrograph which correlates the signal with itself with various time delays, and extracts the frequency spectrum of the signal. → correlator.

Etymology (EN): Autocorrelator, agent n. from → autocorrelate + → -or.

Etymology (PE): Xod-hambâzângar, agent n. from xod-, → auto-,

• hambâzângar, → correlator.

The → covariance of a → time series overt time.

See also: → auto-; → covariance.

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.

See also: → autocovariance; → function.

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

Etymology (EN): 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.”

Etymology (PE): Xodrâhbar from xod-, → auto + râhbar “guide,” from râh “way” + bar, from bordan “to lead.”

The act or process of guiding a telescope automatically.

See also: → autoguider.

Having a self-acting or self-regulating mechanism.

Etymology (EN): From Gk. automatos “self-acting,” from → auto- + matos “willing,” from PIE *men- “to think;” compare with Av./O.Pers. man- “to think.”

Etymology (PE): Xodkâr from xod-, → auto-, + kâr “acting, actor,” from kardan “to do, act.”

A telescope developed to perform photometric observations automatically.

See also: → automatic; → photometric; → telescope.

An → isomorphism between an → object and itself.

See also: → 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).

See also: 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).

See also: → 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.

Etymology (EN): O.Fr., from L. autumnus, a word probably of Etruscan origin.

Etymology (PE): 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.

See also: → 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.

See also: → autumn; → -al; → equinox.