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

An entity that does not exist in space or time and is not perceptible. Some examples are universals, sets, geometrical figures, and numbers.

→ abstract; → object.

An → astronomical object which has not been catalogued.

→ anonymous; → object.

A naturally occurring physical entity or association that lies beyond the Earth's atmosphere and can be studied observationally. In other words, a gravitationally bound structure that is associated with a position in space, but may consist of multiple independent astronomical objects. A list of astronomical objects includes → planets, → asteroids, → comets, → stars, → nebulae, galaxies (→ galaxy), → galaxy clusters, → pulsars, and → black holes. Note that → celestial body, → celestial object, and → heavenly body are less technical terms for these entities.

→ astronomical; → object.

An extraterrestrial → object whose physical properties and formation are studied in → astrophysics.

→ astrophysical; → object.

A compact infrared source in the Orion molecular cloud (OMC-1). It is thought to be a very dusty compact H II region surrounding a young B0 or B1 star.

After Eric Becklin (1940-), and Gerry Neugebauer (1932-) who discovered the object in 1967; → object.

A member of a family of → quasars, or extragalactic → Active Galactic Nuclei, which displays a high radio emission and/or important optical variability over a short period of time. BL Lac objects appear star-like but their spectrum is flat, and partially polarized. Also called → blazars.

BL Lac, from object BL in the constellation → Lacerta (BL Lacertae). The reason for this terminology is that it was originally thought to be an irregular variable star in our Galaxy; hence its variable star designation. In the 1970s the "star" was identified with a bright, variable → radio source and a very faint galaxy; → object.

→ astronomical object.

→ celestial; → object.

An → X-ray source detected close to the center of young → supernova remnant (SNR)s that has no apparent emission in other wave-bands and no binary companions. Although these sources have been known and studied for several decades without much understanding of their nature, exciting results over the past few years have brought them into the forefront of → neutron star studies. They have soft, exclusively thermal spectra in the few hundred eV range and X-ray luminosities around 10³³ - 10³⁴ erg s^-1. About ten CCOs are presently known, including the central sources of CasA, Puppis A and Kes 79 supernova remnants. Several, J1852+0040 in Kes79, J0822.0-4300 in Puppis A and 1E 1207.4-5209 in PKS 1209-51/52, have detected pulsations in the hundreds of milliseconds range. J1852+0040 has a detected → period derivative, indicating that it is spinning down like a → rotation-powered pulsar (RPP). The measured period and either measurements or constraints on period derivative indicate that these sources have very low → magnetic fields in the range 10¹⁰ - 10¹¹ G assuming magnetic dipole braking. Since their SNRs are all young, ~ 10³ - 10⁴ yr, they were probably born with unusually low magnetic fields, which makes them "anti-magnetars" (A. K. Harding, 2013, Front. Phys. 8, 679 and references therein).

→ compact; → central; → object.

An astronomical object that is substantially denser or more compact than most objects of its class. More specifically, a → neutron star or a → stellar black hole.

→ compact; → object.

A word or group of words representing the person or thing upon which the action of a verb is performed or toward which it is directed. In English, generally coming after the verb, without a preposition. In He saw it the pronoun it is the direct object of saw (Dictionary.com).

→ direct; → object.

An astronomical object such as a → variable star, a → nova, a → young stellar object, etc. characterized by abrupt changes of luminosity.

→ eruptive; → object.

An object whose angular size exceeds the resolution of the instrument used to observe it.

→ extended; → object.

An astronomical object that is seen in the direction of a group but not physically belonging to the group. → field galaxy.

→ field; → object.

A population of → substellar objects which are not bound to stars; they are detected in young star clusters. Their masses, estimated from their fluxes, is several Jupiter masses, lower than those of → brown dwarfs. Their formation is not yet explained. Among the envisaged possibilities: 1) These objects form like stars, from protostellar core collapse and subsequent accretion; 2) they form as low-mass members of small groups, and are ejected from the group; 3) they form like planets within circumstellar disks of higher-mass objects, but are ejected either due to internal dynamics or external interactions.

→ free; floating, from M.E. float, from O.E. flotian "to float" (cf. O.N. flota, M.Du. vloten); → object.

Barâxt, → object; šenâvar "that swims, floats," from šenâ "swimming;" Mid.Pers. šnâz "swim," šnâzidan "to swim;" Av. snā- "to wash, swim;" cf. Skt. snā- "to bathe, to wash;" L. nare, natare "to swim" (Fr. nage, nager, natation; Sp.nadar, natacion).

A member of a class of → pre-main sequence stars that experience dramatic changes in magnitude and → spectral type. During an outburst the luminosity of such an object can increase by several orders of magnitude on short time-scales (few months to few years). The phenomenon is explained by abrupt mass transfer from an → accretion disk to a young, low mass → T Tauri star (accretion rates 10^-4 to 10^-3 solar masses per year). → EX Lupi; → Z CMa.

F and U, alphabet letters; Orionis, → Orion; → object.

A small patch of → nebulosity in a → star-forming region, created when fast-moving → jets of material (with speeds up to about 1000 km per sec) from a newborn star collide with the → interstellar medium.

→ Herbig AeBe star; Guillermo Haro (1913-1988), who first in 1940s studied these objects in detail and recognized that they were a by-product of the star formation process; → object.

A galaxy or quasar having a → redshift larger than about 0.8, corresponding to a → look-back time half the present age of the Universe. The qualifier "high" is, however, relative and depends on context and authors' assessment.

→ high; → redshift; → object.

A word or group of words representing the person or thing with reference to which the action of a verb is performed. In English generally coming between the verb and the direct object and paraphrasable as the object of a preposition, usually to or for, following the direct object, as the boy in He gave the boy a book (Dictionary.com).

→ indirect; → object.

A → near-Earth object whose → orbit lies always inside Earth's orbit.

→ inner; → Earth; → object.

A body other than a → star or → substellar object located in → interstellar space and not → gravitationally bound to a star. Its → hyperbolic orbit would indicate an object not bound to the Sun. The first known ISO is → 1I/'Oumuamua. ISOs are icy → planetesimals that are expected to behave like the → long-period comets of the solar system; volatile ices sublimate when the ISO approaches the Sun, developing a → coma and a → dust tail -- features that should make them bright and therefore easy to spot. The rocky ISOs, on the other hand, only reflect sunlight. As their → albedo is expected to be extremely low they become dark (after eons of bombardment by high-energy cosmic rays), they would be extremely faint and hard to detect (Hainaut et al., 2018, The Messenger 173, 13).

→ interstellar; → object.