horizontal branch (HB)
šâxe-ye ofoqi (#)
Fr.: branche horizontale
A set of roughly horizontal points in the → Hertzsprung-Russell diagram of a typical → globular cluster. It displays a stage of stellar evolution which immediately follows the → red giant branch (RGB) in stars with an initial mass < 1.2 Msun. When the star's ascent of the RGB is terminated by the → helium flash, it moves down to the HB. The star's → effective temperature on the HB is higher than it was on the RGB, but the luminosity is considerably less than at the helium flash. Usually HB stars have two energy sources: in addition to the → helium burning in their cores, they experience → hydrogen fusion in a surrounding shell. The thickness of the shell determines the color of the HB stars. A thin shell, involving low → opacity, makes the star look blue. The HB domain encompasses a very large effective temperature range with several members: → extreme HB, → blue HB, → RR Lyrae, → red HB, and → red clump stars. The locations depend on many parameters, including stellar mass, metallicity, age, helium abundance, and rotation.
horizontal branch star
setâre-ye šâxe-ye ofoqi
Fr.: étoile de la branche horizontale
A star lying on the → horizontal branch.
A type of → lunar eclipse that occurs when both the Sun and the eclipsed Moon can be observed at the same time. This is possible only when lunar eclipse occurs just before sunset or just after sunrise. At that case, both bodies will appear just above the horizon at nearly opposite points in the sky. Also called → selenelion and → selenehelion.
Fr.: parallaxe horizontale
The angle under which the radius of the Earth at the place of observation would be seen from a celestial body when it is in the horizon (at the instant of rising or setting). The amount varies with the latitude since the Earth is not exactly spherical, and is greatest at equator.
šekast-e ofoqi (#)
Fr.: réfraction horizontale
The angular distance of an object below the horizon when it appears to lie on the horizon.
In computer science, a scaling in which the processing power is increased/decreased by adding/removing nodes with similar resources. See also → vertical scaling.
1) šâx; 2) šâxak; 3) karnâ
Fr.: 1) corne; 2) cornet; 3) cor
1a) The bony pointed outgrowth, usually in pairs, on the heads of some animals.
M.E. horn(e), from O.E. horn "horn of an animal," also "wind instrument" (originally made from animal horns), from P.Gmc. *khurnaz (cf. Ger. Horn, Du. horen), from PIE *ker- "head, horn, top, summit" (cf. Pers. soru "horn," sar "head," Gk. kara "head," karena "head, top," keras "horn;" L. cornu "horn," cerebrum "brain;" Skt. śiras- "head, chief").
1, 2) Mid.Pers šâk; cf. Skt. sakha- "a branch,
a limb;" Arm. cax; Lith. šaka; O.S. soxa;
PIE *kakhâ "branch."
The Clock. A faint constellation in the southern hemisphere, at about 3h right ascension, 55° south declination. Its brightest star, α Horologii, is of magnitude 3.9. Abbreviation: Hor; Genitive: Horologii.
Horologium "clock," from
L., from Gk. horologion, from horolog(os) "timeteller,"
from horo-, combining form of hora "hour" (→ year)
stem of legein "to speak, tell" (+ -os adj. suffix) + -ion
Sâ'at "clock," from Ar.
A schematic drawing showing the positions of the Sun, Moon, and planets at the time of a person's birth for baseless astrological purposes.
From M.Fr. horoscope, from L. horoscopus, from Gk. horoskopos "nativity, horoscope," also "one who casts a horoscope," from hora "hour" + skopos "watching."
Zâyecé "horoscope, thema," from Mid.Pers. zâycag "horoscope," from zâyidan, zâdan, "to give birth, bring forth;" Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" cf. Skt. jan- "to produce, create; to be born," janati "begets, bears;" Gk. gignomai "to happen, become, be born;" L. gignere "to beget;" PIE base *gen- "to give birth, beget."
1) asb (#); 2) asbak (#)
1) A large, solid-hoofed, herbivorous quadruped, Equus caballus,
domesticated since prehistoric times.
Horse, O.E. hors, from P.Gmc. *khursa- (cf. M.Du. ors, Du. ros, O.H.G. hros, Ger. Roß "horse"), of unknown origin; → latitude.
Asb "horse," from Mid.Pers. asp; O.Pers. asa- "horse;" Av. aspa- "horse," aspā- "mare," aspaiia- "pertaining to the horse;" cf. Skt. áśva- "horse, steed;" Gk. hippos; L. equus; O.Ir. ech; Goth. aihwa-; O.E. eoh "horse;" PIE base *ekwo- "horse."
Fr.: calmes tropicaux, latitudes des chevaux
The belts of latitude over the oceans, located around 30° north and south of the equator, characterized by predominantly calm or light winds and hot and dry weather.
→ horse; → latitude.
Horsehead Nebula (NGC 2024)
miq-e sar-e asb, ~ asbsar
Fr.: nébuleuse de la Tête de Cheval
A huge → dark cloud of → interstellar dust that is shaped like a horse's head. It is luminous at its edges because it is in front of the bright → emission nebula IC 434. Its height and width are about 5 and 2.5 → light-years respectively. It is located at a distance of about 1500 light-years in the constellation → Orion. Also known as Barnard 33.
asb-e boxâr (#)
A unit that is used to measure the → power of engines and motors.
Fr.: monture en fer de cheval
An equatorial mounting in which the upper end of the polar axis frame is made into a horseshoe shape to accommodate the telescope tube.
Barnešând, → mounting; na'l "horseshoe, shoe," loanword from Ar.
Fr.: orbite en fer à cheval
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.
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").
kahkešân-e mizbân (#)
Fr.: galaxie hôte
A usually faint galaxy in which a remarkable phenomenon, such as a → supernova event, occurs.
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 (
hot accretion flow
tacân-e farbâl-e dâq
Fr.: écoulement d'accrétion chaud
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.