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25 Orionis group
goruh-e 25-Šekârgar, ~ 25-Oryon
Fr.: groupe de 25 Orionis
A group of nearly 200 low-mass → pre-main-sequence stars, concentrated within ~ 1 of the early → B star → 25 Orionis, in the component a of the → Orion OB1 Association. The group also harbors the → Herbig Ae/Be star V346 Ori and a dozen other early-type stars. The velocity distribution for the low-mass stars shows a narrow peak at 19.7 km s-1, offset ~ 10 km s-1 from the velocity characterizing the younger stars of the Ori OB1b subassociation, and 4 km s-1 from the velocity of widely spread young stars of the Ori OB1a population. This indicates that the 25 Ori group is a distinct kinematic entity. The low-mass members follow a well-defined band in the → color-magnitude diagram, consistent with an age of ~ 7-10 Myr (Briceno et al., 2007, ApJ 661, 1119).
→ 25 Orionis; → group.
Amalthea [Jupiter V]
The third of Jupiter's known satellites orbiting at about 181,300 km from Jupiter with a period of about 12h. A mean diameter of 189 km makes it the fifth largest satellite of Jupiter. Amalthea was discovered by E. Barnard in 1892.
Amalthea, in Gk. mythology, the goat that suckled Zeus after his mother had him sent to Crete so his father would not eat him.
Ananke [Jupiter XII]
The thirteenth of Jupiter's known satellites discovered by S.B. Nicholson in 1951. It orbits the planet at a mean distance of 21,200,000 km, and has a diameter of about 30 km.
In Gk. mythology, Ananke is the personification of destiny, unalterable necessity and fate; she is also the mother of Adrastea,
A copy of computer files that is stored separately from the original in order to protect against loss of data.
Backup "substitute, support," from → back + up.
Poštvân "prop, support, help" from pošt, → back, + -vân suffix denting protection, variant of -bân.
barnâme-ye yadaki (#)
Fr.: programme de remplacement
An auxiliary observing program to be carried out at telescope in case the atmospheric conditions make the main program unfeasible.
Backup, from → back + up; → program.
Barnâmé, → program; yadaki "reserve, substitute," from yadak "a led horse."
binary supermassive black hole
siyah-câl-e abar-porjerm-e dorin
Fr.: trou noir supermassif double
A → dual supermassive black hole whose components are separated by a few parsecs.
→ binary; → supermassive; → black; → hole.
Fr.: supergéante bleue
An evolved star of spectral type O, B, or A; e.g. → Rigel, → Deneb.
→ blue; → supergiant.
bottom-up structure formation
diseš-e sâxtâr az pâyin bé bâlâ
Fr.: formation des structures du bas vers le haut
A → structure formation scenario in which small galaxies form first, and larger structures are then formed in due course. Contrary to → top-down structure formation.
Fr.: vitesse de rupture
The velocity of a → rotating star at which the → centrifugal force equals the → gravitational force. Also known as → critical velocity. The simplest expression of the break-up velocity for an OB star, ignoring the → Eddington luminosity, is given by the relation: v = (GM / R)1/2, where M and R are the mass and radius of the star respectively, and G the → gravitational constant. A more realistic expression takes into account not only the → radiation pressure, but also the non-uniformity of the brightness over the stellar surface, as indicated by → von Zeipel theorem. With these conditions, the break-up velocity has a more complicated formula, corresponding to the velocity reached when somewhere on the star the → total gravity becomes zero.
Callisto (Jupiter IV)
The eighth of → Jupiter's known moons and the second brightest and the outermost of the four → Galilean satellites. With a diameter of 4800 km (0.38 Earths), Castillo is roughly the same size as Mercury. It orbits Jupiter in 16.689 days at a distance of 1,883,000 km from the planet, beyond Jupiter's main → radiation belts. It is the third largest moon in the entire solar system. Its mass is 10.76 × 1022 kg (about 1.5 Earth Moons) and its mean → surface temperature is -155 °C. The most prominent feature of Callisto is its craters, as it has the most craters of any object in the solar system. Due to its orbit being further away from Jupiter, it is not under the same → tidal heating influences as → Io, → Europa, or → Ganymede. Callisto's thin → atmosphere is composed of → carbon dioxide and likely some → molecular oxygen. Callisto is thought to have formed as a result of slow → accretion from the → protoplanetary disk of gas and dust that surrounded Jupiter after its formation.
Callisto, an attendant of Artemis in Greek mythology. Because of her love affair with Zeus, she was transformed into a bear by Artemis. According to another legend she was changed into a bear by the jealous Hera. Zeus transferred her to the heavens as the → constellation → Ursa Major (great bear).
canonical upper limit
hadd-e zabarin-e jerm
Fr.: limite supériure canonique
A physical upper mass limit near 150 Msun assumed for the stellar → initial mass function (Kroupa et al. 2012, arXiv:1112.3340).
goruh-e karbonil (#)
Fr.: groupe carbonyl
The radical -C=O, which occurs in several compounds, such as → aldehydes and ketones.
From → carbon + -yl a suffix used in the names of some radicals; → group.
Carme (Jupiter XI)
The fourteenth of Jupiter's known satellites; 40 km in size; → retrograde orbit. It was discovered by Nicholson in 1938.
In Gk mythology, Carme was a wife of Zeus, and the mother of Britomartis, a Cretan goddess.
Fr.: superamas du Centaur
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.
Fr.: pic central
Same as → central peak.
charge-coupled device (CCD)
dastgâh-e jafsari-ye bâr, sisidi
Fr.: dispositif à transfert de charge
A solid-state detector that stores the electrons, produced by incident photons, in potential wells at the surface of a semiconductor. The packages of charge are moved about the surface by being transferred to similar adjacent potential wells. The wells are controlled by the manipulation of voltage applied to surface electrodes.
Fr.: suppression de Compton
In → gamma ray → spectroscopy, a technique to reduce the contribution of gamma rays generated by → Compton scattering.
→ Compton; → suppression.
abar-novâ-ye rombeš-e maqzé, abar-now-axtar-e ~ ~
Fr.: supernova à effondrement de coeur
A supernova arising from the → core collapse of a → massive star. Same as → Type Ib, → Type Ic, or → Type II supernova.
1) joft (#), 2) joftniru (#); 3) joftidan (#), jafsar kardan
Fr.: 1, 2) couple; 3) coupler
1) General: Two items of the same kind; a pair; something that joins or connects
two things together; a link.
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,"
Mid.Pers. jug, ayoxtan "to join, yoke,"
Mod.Pers. yuq "yoke,"
cf. Skt. yugam "yoke,"
Gk. zygon "yoke," zeugnyanai "to join, unite,"
L. jugare "to join," from jugum "yoke,"
P.Gmc. *yukam, E. yoke;
PIE *yeug- "to join."
Joined together, connected by a link. → coupled system, → charge-coupled device.
Adj. from → couple.
Jafsar "connected, joined pair," in Tâleši, from jaf, variant of joft, as above + sar "head," literally "joined by head" (Mid.Pers. sar, Av. sarah- "head," Skt. siras- "head," Gk. kara "head," keras "horn," Mod.Pers. sarun "horn," L. cerebrum "brain;" PIE *ker- "head, horn"); joftidé adj./p.p. from joftidan, → couple.
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