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

The mixture of gases of which the earth's atmosphere is composed. It is chiefly made up of Nitrogen (about 78%) and Oxygen (about 20%).

Air, from O.Fr. air, L. aer, Gk. aer, related to Gk. aura "breath, vapor;" PIE *wer- "to raise, lift."

Havâ, from Ar., probably a loanword from Mid.Pers. vây "weather," Av. vayah-, vaya- "weather, atmosphere," from va- "to blow." Cf. Skt. va-, Gk. aemi- "to blow;" Av. vâta- "wind," Skt. vata-, L. ventus, Mod. Pers. bâd "wind." PIE *we- "to blow".

Same as → cosmic-ray shower.

→ air; → shower.

A machine capable of flying by means of → buoyancy or → aerodynamic forces, such as an airplane, helicopter, glider, or balloon.

→ air; → craft.

The faint ever-present glow in the → night time → sky caused by the → collision of → atoms and → molecules in Earth's → upper atmosphere with high energy → particles and → radiation, mainly from the → Sun. The airglow, also called nightglow, varies with time of night, → latitude, and → season.

→ air; → glow; → night.

A measure of the path length traversed by starlight through Earth's atmosphere before it reaches the detector; it is taken relative to the length at the zenith.

→ air; → mass.

The bright disk-like image of a point source of light, such as a star, as seen in an optical system with a circular → aperture.

Named after Sir George Biddell Airy (1801-1892), Astronomer Royal, great administrator, who much improved the equipment at Greenwich Observatory. → disk.

Gerdé, → disk; Airy, see above.

A → transit circle that defines the position of the → Greenwich Meridian since the first observation was taken with it in 1851. Airy's transit circle lies at longitude 0°, by definition, and latitude 51° 28' 38'' N.

Named after Sir George Biddell Airy (1801-1892), Astronomer Royal, at the Royal Observatory in Greenwich from 1835 to 1881. Airy transformed the observatory, installing some of the most advanced astronomical apparatus of his day and expanded both staff numbers and their workload; → transit; → circle.

The brightest star in → Aquila (apparent visual magnitude 0.77), and the twelfth brightest star in the sky. Altair is a whitish A7 → main sequence star. It has one of the fastest known rotational speeds, 242 km/s at the equator, compared with the Sun's about 2 km/s.

Altair, from Ar. An Nasr at-Taiir "The Flying Vulture," from Nasr "vulture" + Ta'ir "flying."

Karkas-e Parandé "The Flying Vulture" coined by Biruni (around A.D. 1000), from karkas "vulture," Av. kahrkâsa- "devourer hen," from *kahrka "hen" (Mod.Pers. kark "hen," karak "quail") + *âsa "to eat" (Mod.Pers. âš "food, soup") + Parandé "flying," from paridan "to fly" (from Mid./Mod.Pers. par(r) "feather, wing," Av. parəna- "feather, wing;" cp. Skt. parna "feather," E. fern; PIE *porno- "feather").

→ Coma Berenices.

Air whose density is increased by being subjected to a pressure greater than atmospheric pressure.

→ compressed; → air.

A system of two perpendicular fine threads of wire placed in the focus of the eyepiece of an optical instrument and used as a sighting reference.

→ cross; → hair.

Târbast, from târ + bast. The first component târ "thread, string, wire," cognate with tanidan, tan- "to spin, twist, weave," → tension; the second component bast "to bind; to arrange" (past stem of bastan, from Mid.Pers. bastan/vastan "to bind, shut," → band.

The simultaneous formation of an → electron and a → positron in the → pair production process.

→ electron; → positron; → pair.

1) Any of the numerous fine filaments growing from the skin of humans or animals.
2) A mass or aggregate of hairs covering the human head. The mean diameter of human hair is about 100 μm (from 17 to 181 μm)
3) An outgrowth of the epidermis of a plant.
→ crosshairs; → no hair theorem; → Berenice's Hair.

M.E. heer; O.E. hær; cf. O.H.G. har, Du. haar, Ger. Haar "hair;" PIE base *kaisaro- "hair," from *ker(s)- "to bristle;" cf. Skt. kesara- "hair, mane (of a horse or lion)."

Mu(y) "hair;" Mid.Pers. môy "hair."
Gis, gisu, from Mid.Pers. ges, gesuk "hair, lock, tress," Av. gaêsa- "curly hair," gaêsav-, gaêθav- "curly, curly-haired," cf. Gk. kaite "bushy hair, mane," O.Ir. gaiset, PIE *ghaites "curly hair."

There are only three parameters that can be applied by an outside observer relating to a → black hole: → mass, → electric charge, and → angular momentum. The collapse of a star into a black hole wipes out all other details of its structure, and the observer can never discover any other properties of the star which formed the black hole. In other words, none of its characteristics leave any trace outside the black hole, and that is what is meant by "hair."

No, M.E., from O.E. na "never, no," cognate with Pers. na, nâ, → non-; → hair; → theorem.

Farbin, → theorem; bimuyi, noun from bimu "without hair," from bi- "without" (→ in-) + mu, → hair.
Kacali "baldness," from kacal "bald," also "crooked, bandy-legged," from kajal, from kaj "crooked, curved, bent" + → -al; probably unrelated to kal "bald," → colure.

1) Something consisting of or regarded as having two parts or pieces joined together. → pair annihilation; → pair production.
2) Two identical, similar, or corresponding things.

M.E., from O.Fr. paire, from L. paria "equals," neuter plural of par (genitive paris) "a pair, counterpart, equal."

1) Joft "pair, couple," Lori, Laki jeft, Qâyeni jof, Tabari jeft, Mid.Pers. yuxt "pair, couple," Av. yuxta- "a team of horses," from yaog- "to yoke, harness, put to; to join, unite," infinitive yuxta, Mid.Pers. jug, ayoxtan "to join, yoke," Mod.Pers. yuq "yoke;" cf. Skt. yuga- "yoke," Gk. zygon "yoke," zeugnyanai "to join, unite," L. jugare "to join," from jugum "yoke," P.Gmc. *yukam, E. yoke; PIE *yeug- "to join."
Hamâl, from ham- "together, with; same, equally, even" (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- "one and the same;" Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + suffix -âl, → -al.

Mutual destruction of a particle and its antiparticle, such as an electron-positron pair, when they collide. The total energy of the two particles is converted into energy as gamma rays. It is the inverse process to → pair production.

→ pair; → annihilation

An instability arising from the → pair production inside a → massive star leading to energetic → supernova explosions. The pair instability occurs when, late in the star's life, the core reaches a sufficiently high temperature after → carbon burning, a condition in which the pair production can take place. The pairs of electron and positron annihilate to form a neutrino and an anti-neutrino. Consequently, the pressure drops and the outer layers fall in onto the core. The temperature and pressure increase rapidly and eventually titanic nuclear burning causes an extraordinary explosion with energies higher than 10⁵¹ erg. See also → pair-instability supernova and → pulsational pair-instability supernova.

→ pair; → instability.

The creation of an → elementary particle and its → antiparticle from a → boson. For example, the formation of an → electron and a → positron in the interaction of high-energy → gamma ray photons, having at least 1.02 Mev, with an → atomic nucleus (γ → e^- + e⁺). The → rest masses of the electron and positron being 0.51 MeV each, the excess energy will be carried away by these two particles. Pair production is the inverse process to → pair annihilation.

→ pair; → production

→ pair instability

→ pair; → instability.

A special type of → supernova that would result from the → pair instability in → supermassive stars with a mass range between 140 and 260 Msun in a low → metallicity environment. Such objects descended from the → Population III stars in the early history of the Universe. Such supernovae are the most powerful thermonuclear explosions in the Universe. Pair-instability supernovae may have played an important role in the synthesis of → heavy elements. Moreover, the energetic feedback of the processed elements to their surroundings could have affected the structure and evolution of the early Universe (See, e.g., Fryer et al. 2001, ApJ 550, 372; Heger & Woosley 2002, ApJ 567, 532). See also → pulsational pair-instability supernova.

→ pair; → instability; → supernova.