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

An equatorial mounting in which the upper end of the polar axis frame is made into a horseshoe shape to accommodate the telescope tube.

Horseshoe, from → horse + shoe, from O.E. scoh "shoe," from P.Gmc. *skokhaz (cf. Dan., Swed. sko, O.S. skoh, Du. schoen, O.H.G. scuoh, Ger. Schuh); → mounting.

Barnešând, → mounting; na'l "horseshoe, shoe," loanword from Ar.

A periodic orbit which passes around the → Lagrangian points L4, L3, and L5, but neither of the two primaries. This orbit is shaped like a horseshoe when viewed in a reference frame rotating with the primaries. Such orbits occur in the solar system, for example in the case of the satellites → Janus and → Epimetheus, which share the same orbit around → Saturn. The smaller Epimetheus encompasses both the L4 and L5 points associated with the larger Janus and performs a horseshoe orbit relative to Saturn and Janus. The satellites experience a close approach every 4 years during which their orbits are exchanged. → tadpole orbit.

→ horseshoe mounting; → orbit.

A flexible → pipe for conveying a → liquid.

M.E., O.E. akin to Du. hoos, O.N. hosa, Ger. Hose.

Šilang, probably loan from Russ. шлаиг (shlang) "hose."

One that receives or entertains guests especially in his own home. → host galaxy.

M.E. (h)oste, from O.Fr. hoste "guest, host," from L. hospitem (nom. hospes) "guest, host," lit. "lord of strangers," from hostis "stranger."

Mizbân "host," from Mid.Pers. mezdbân "host," from mêzd "offering, meal," Mod.Pers. miz "guest; offering; meal" + -bân a suffix denoting "keeper, guard," sometimes forming agent nouns or indicating relation (e.g. keštibân "sailor;" bâdbân "a sail;" mehrabân "affectionate;" mizbân "host;" âsiyâbân "a miller;" bâqbân "gardener"). This suffix derives from O.Pers. -pāvan- (as in xšaça.pāvan- "satrap"); Av. -pāna- (as in pəšu.pāna- "keeping the passage, bridge guard"), from Proto-Iranian *pa- "to prtotect, keep," → observe, + suffix *-van-; cf. Skt. -pāna- (as in tanū.pāna- "protection of the body").

A usually faint galaxy in which a remarkable phenomenon, such as a → supernova event, occurs.

→ host; → galaxy.

Having a relatively high temperature. → hot accretion flow, → hot core, → hot corino, → hot dark matter , → hot dust-obscured galaxy, → hot Jupiter, → hot molecular core, → hot pixel, → hot star.

Hot, O.E. hat, "hot; fervent, fierce," from P.Gmc. *haitoz (cf. Du. heet, Ger. heiß "hot," Goth. heito "heat of a fever").

Dâq "hot; brand, marking," from Mid.Pers. dâq, dâk "hot," dažitan "to burn, scorch," dažišn "burning" (Mod.Pers. dežan (دژن) "acid, pugnent"), from Av. dag-, daž- "to burn;" cf. Skt. dah- "to burn;" L. fovere "to warm, heat; " Arm. dažan "violent, wild;" Lith. degu "to burn;" O.E. fefor; E. fever. PIE base *dhegh- "to burn."

A type of → accretion flow by a → compact object such as a → black hole which has a high → virial temperature, is → optically thick, and occurs at lower mass → accretion rates compared with → cold accretion flows. In a hot accretion flow with a very low mass accretion rate, the electron mean free path is very large, and so the accreting → plasma is nearly collisionless. In this type of accretion flow, thermal conduction transports the energy from the inner to the outer regions. As the gas temperature in the outer regions can be increased above the → virial temperature , the gas in the outer regions can escape from the gravitational potential of the central black hole and form outflows, significantly decreasing the mass accretion rate.

→ cold; → accretion; → flow.

Same as → hot molecular core.

→ hot; → core.

A warm, compact → molecular clump found in the inner envelope of a → Class 0 → protostar. Hot corinos are low-mass analogs of → hot molecular cores (HMCs) occurring in → massive star formation sites. With a typical size of ≤ 150 → astronomical units, hot corinos are two orders of magnitude smaller than HMCs. They have densities ≥ 10⁷ cm^-3 and temperatures ≥ 100 K (Ceccarelli, C. 2004, ASP Conf. Ser. 323, 195).

→ hot; corino, from → core + -ino a diminutive suffix in It.

Any form of → dark matter which had a significant velocity dispersion (comparable to the velocity of light), when the Universe first became → matter-dominated.

→ hot; → dark; → matter.

A member of the most extreme galaxies in terms of their luminosities and unusual hot → dust temperatures. The → infrared emission from HDOGs is dominated by obscured accretion onto a central → supermassive black hole (SMBH), in most cases without significant contribution from → star formation. The large contrast between the underlying → host galaxy and the hyper-luminous emission from the → active galactic nucleus (AGN) implies that either the SMBH is much more massive than expected for the stellar mass of its host, or is radiating well above its → Eddington limit. The most extreme of these remarkable systems known is → W2246-0526.

→ hot; → dust; → obscure; → galaxy.

Same as → Schottky diode

→ hot; → electron; → diode.

A giant, gaseous, Jupiter-like planet lying too close to its parent star and having an orbital period from a few days to a few weeks. The existence of hot Jupiters is usually interpreted in terms of planetary migration. These planets can, in principle, be formed at larger distances from their stars and migrate to the inner regions due to dynamical interaction with the proto-planetary disk.

→ hot; → Jupiter.

A relatively small, dense, and hot → molecular clump occurring in regions of → massive star formation. HMCs have diameters ≤ 0.1 pc, densities ≥ 10⁷ cm^-3, and temperatures ≥ 100 K. The densest hot cores are traced in → ammonia (NH₃) and possess densities of 10⁸ cm^-3, sizes down to 0.05 pc and temperatures of up to 250 K. Hot molecular cores are generally associated with → compact H II regions and → ultracompact H II regions. High angular resolution observations suggest that HMCs are internally heated by embedded sources, since temperature and density increases toward the center as expected if star formation is occurring close to the core center. Same as → hot core.

→ hot; → molecular; → core.

Of a → CCD detector, a pixel that has higher charge loss. Hot pixels are a type of noise affecting almost every CCD camera. They are caused by small contamination or production faults in the CCD sensor area.

→ hot; → pixel.

A compact, highly luminous region in a cataclysmic binary located in the accretion disk where the stream of material hits it.

→ hot; → spot.

A member of a class of stars having high → effective temperatures (above some 15,000 K); mainly → massive stars, but also including → exciting stars of → planetary nebulae, → white dwarfs, and → symbiotic stars.

→ hot; → star.

The 24th part of a day; 60 minutes.
An angular unit of right ascension, equivalent to 15°.

Hour, from M.E. houre, from O.Fr. hore, from L. hora "hour, time, season," from Gk. hora "any limited time," used of day, hour, season, year; cognate E. → year.

Sâ'at, from Ar.

A telescope based coordinate specifying the angle, in the equatorial plane, from the meridian to a plane containing the celestial object and the north and south celestial poles.

→ hour; → angle.

A great circle passing through an object and the → celestial poles intersecting the → celestial equator at right angles.

→ hour; → circle.