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

The angular distance between the → ascending node of an object orbiting the Earth and its perigee, measured from the Earth. See also: → argument of perihelion, → argument of periapsis.

→ argument; → perigee.

The angular distance between the → ascending node of an object orbiting the Sun and its perihelion. Argument of perihelion is measured in the → orbital plane with respect to the Sun and in the direction of motion. It is one of the → orbital elements and usually shown with the symbol ω. See also: → argument of perigee, → argument of periapsis.

→ argument; → perihelion.

A series of experiments carried out in the early 1980s by Alain Aspect and his colleagues that showed the violation of → Bell's inequality. Accordingly, quantum phenomena cannot be described by the → hidden variable theories, contrarily to the → EPR paradox interpretation.

Alain Aspect (1947-); → experiment. Aspect et al., 1982, Physical Review Letters, Vol. 49, No. 25 and references therein.

1) Roughness or unevenness of surface.
2) Physics: A microscopic projection on a metal surface resulting from normal surface finishing processes.
3) Geology: A site on a → fault surface where the two sides are held together by an area of higher strength than the areas surrounding it. When the stress on the fault exceeds the strength of the asperity, the asperity fails as an → earthquake.

M.E. asperite, from O.Fr. asperité "difficulty, painful situation," from L. asperitas, from asper "rough, harsh," of unknown origin.

From zaft "thick, gross, rude," (Steingass, Dehxodâ), + noun suffix -i.

The splitting of starlight into a spectrum in the atmosphere because the atmosphere acts as a refracting prism. This phenomenon brings about a practical problem for spectroscopic observations using a slit. → differential refraction; → atmospheric refraction.

→ atmospheric; → dispersion.

Transfer of microbes and biochemical compounds from a planet to another due to meteoric impacts. Debris being knocked off a planet like Mars can reach escape velocity and enter the atmosphere of another planet with passenger micro-organisms intact.

→ ballistic; → panspermia.

A group of seven stars, an → asterism, lying inside the Northern constellation → Ursa Major. They are: → Dubhe, → Merak, → Phad, → Megrez, → Alioth, → Mizar, and → Alkaid. The group is also known as the Plough in Great Britain.

→ big; dipper a popular U.S. name for the asterism known in Britain as The Plough or Charles' Wain, from dip O.E. dyppan "immerse," from P.Gmc. *dupjanan.

Haft barâdarân "the seven brothers," from haft "seven" (Mid.Pers. haft, Av. hapta, cf. Skt. sapta, Gk. hepta, L. septem, P.Gmc. *sebun, Du. zeven, O.H.G. sibun, Ger. sieben, E. seven; PIE *septm) + barâdarân, plural of barâdar "brother" (Mid.Pers. brad, bardar, O.Pers./Av. brātar-, cf. Skt. bhrátar-, Gk. phrater, L. frater, P.Gmc. *brothar; PIE base *bhrater- "brother").
Haftowrang, Mid.Pers. haptôiring, from Av. haptôiringa- "with seven marks," from hapto- "seven,"as above, + iringa- "mark," cf. Skt. linga- "mark, token, sign."
Camcé "a spoon, ladle; a wooden bowl or cup;" bozorg "big, large."

A mathematical operation that combines two numbers, quantities, sets, etc., to give a third. For example, multiplication of two numbers is a binary operation.
A binary operation * on a set S is → commutative if a * b = b * a for all a, b∈ S.
A binary operation * on a set S is → associative if (a * b) * c = a * (b * c) for all a, b, c∈ S.

→ binary; → operation.

A → dual supermassive black hole whose components are separated by a few parsecs.

→ binary; → supermassive; → black; → hole.

The temperature at which a blackbody would emit the same radiation per unit area as that emitted by a given body at a given temperature.

→ blackbody; → temperature.

An evolved star of spectral type O, B, or A; e.g. → Rigel, → Deneb.

→ blue; → supergiant.

In radio astronomy, the temperature of a source calculated on the assumption that it is a blackbody emitting radiation of the observed intensity at a given wavelength. → antenna temperature.

→ brightness; → temperature.

A period of 76 years after which the new and full moons would return to the same day of the solar year. This was intended as an improvement of the → Metonic cycle because the 6940 days of the Metonic cycle exceeded 19 years by about a quarter of a day, and exceeded 235 → lunations by a larger amount of time.

Named after Calippus of Cyzicus (about 370-300 BC), a Greek astronomer and mathematician.

A physical upper mass limit near 150 Msun assumed for the stellar → initial mass function (Kroupa et al. 2012, arXiv:1112.3340).

→ canonical; → upper; → limit.

An experiment devised to produce → interference patterns from a beam of helium atoms passing through two adjacent apertures, as in → Young's experiment.

Named after O. Carnal and J. Mlynek, who first carried out this experiment in 1991 (Phys. Rev. Lett. 66, 2689); → experiment.

The nearest large → supercluster. It is dominated by the → galaxy cluster A3526 (→ Abell catalog). The Centaurus supercluster is a long structure that stretches away from us. The most distant of the clusters, A3581, is about 300 million → light-years away.

→ Centaurus; → cluster.

The temperature of that black-body which has the same spectral energy distribution in a limited spectral region, as the object under study has.

→ color; → temperature.

A period during which a newly constructed observing instrument is used for test.

→ commissioning; → period.

Same as → complementary screens.

→ complementary; → aperture.

A highly unstable, → very massive star lying just below the empirical upper luminosity boundary in the → H-R diagram (→ Humphreys-Davidson limit) with spectral types ranging from late A to M. Cool hypergiants very likely represent a very short-lived evolutionary stage, and are distinguished by their high → mass loss rates. Many of them also show photometric and spectroscopic variability, and some have large → infrared excesses and extensive circumstellar ejecta. The evolutionary state of most of these stars is not known but they are all → post-main-sequence stars (Humphreys, 2008, IAUS 250).

→ cool; → hypergiant.