miq-e Šekârgar, ~ Oryon
Fr.: Nébuleuse d'Orion
The best known → ionized nebula and one of the nearest regions to the Sun in which stars are presently being formed. It is visible to the naked eye in the constellation → Orion south of → Orion's Belt as a fuzzy patch. It lies about 1,500 → light-years away and measures about 30 light-years across. The Orion Nebula is ionized and made visible by a small group of → O-type and → B-type stars known as the → Trapezium cluster. Other designations: M 42, NGC 1976. See also: → Orion molecular cloud; → Huygens Region ; → Orion association; → Orion Bar; → Orion Bright Bar.
Orion OB1 Association
âhazeš-e OB1 Šekârgar, ~ ~ Oryon
Fr.: Association Orion OB1
An → OB association consisting of several
dozen → hot stars
of → spectral types O and B
(→ O star, → B star).
The Orion OB1 association consists of several subgroups, first
divided by Blaauw (1964) into four subgroups. The subgroups differ
in age and gas and dust content:
Fr.: éperon d'Orion
Same as → Orion Arm.
kamarband-e Šekârgar, ~ Orion
Fr.: Ceinture d'Orion
Three prominent stars in the central regions of the constellation → Orion that align to form the "belt" of the mythological Hunter. They are → Alnitak (ζ Ori), → Alnilam (ε Ori), and → Mintaka (δ Ori). The easternmost star Alnitak is separated from the middle one, Alnilam, by 1°.36, and the westernmost Mintaka has an angular distance of 1°.23 from Alnilam. Their distance is between 800 and 1,300 → light-years from Earth. They probably formed inside the same → molecular cloud less than 10 million years ago.
Šamšir-e Šekârgar, ~ Oryon
Fr.: Epée d'Orion
An astronomical → asterism in the constellation → Orion forming an almost vertical line beneath → Orion's Belt. From north to south, the most prominent objects in the Sword are the cluster NGC 1981, the star → 42 Orionis, the famous → Orion Nebula, and the Sword's brightest star → Iota Orionis (→ Hatsya). None of these objects is particularly bright in itself, but their proximity to one another and the nebulosity across much of this region makes the Sword stand out clearly in the night sky.
Fr.: bras Orion-Cygne
Same as → Orion Arm.
A meteor shower that appears to emanate from the constellation → Orion. It peaks between October 14 and 20 with about 20 meteors per hour.
1) A child who has lost both parents through death, or, less commonly, one parent.
M.E., from L.L. orphanus "destitute, without parents," from Gk. orphanos "bereaved;" akin to L. orbus "bereaved," Skt. arbhah "weak, child," Armenian orb "orphan," O.Irish orbe "heir," O.C.S. rabu "slave," Ger. Erbe, O.E. ierfa "heir," O.H.G. arabeit, Ger. Arbeit "work," O.E. earfoδ "hardship, suffering, trouble."
Yatim "fatherless," from Ar.
Fr.: proto-étoile orpheline
A → protostellar object which has been dynamically ejected from a newborn → multiple star system, either into a tenuously bound orbit or into an escape, thus depriving it from gaining much additional mass. Recent observations have shown that → Class I protostellar sources have a population of distant companions at separations ~ 1000 to 5000 → astronomical unit (AU)s. Moreover, the companion fraction diminishes as the sources evolve. According to N-body simulations of unstable → triple systems embedded in dense cloud cores, many companions are ejected into unbound orbits and quickly escape, but others are ejected with insufficient momentum to climb out of the potential well of the cloud core and associated binary. These loosely bound companions reach distances of many thousands of AU before falling back and eventually being ejected into escapes as the cloud cores gradually disappear (B. Reipurth et al. 2010, arXiv:1010.3307).
A mechanical device that illustrates the relative positions and motions of the planets and moons in the solar system in heliocentric model.
Named after Charles Boyle, 4th Earl of Orrery (1676-1731), for whom the device was first made.
Prefix denoting right, straight, correct.
Ortho-, from Gk. orthos "set upright, straight, true, correct, regular;" cf. L. arduus "high, steep," O.Ir. ard "high;" also cognate with Av. ərəduua-, as below; from PIE *eredh- "high."
Ardâ-, from Av. ərəduua- "upright, erect, risen;" cf. Skt. ūrdhvá- "upright, tending upward, high;" Gk. ortho, as above.
Fr.: eau ortho
The → water molecule in which the → nuclear spin of the constituent → hydrogen atoms are → parallel (→ orthohydrogen). In astrophysics the ratio between ortho- and → para-water is used to determine temperatures in → interstellar medium.
In elementary geometry, pertaining to or involving right angles or perpendiculars.
Ardâkonj, from ardâ-, → ortho-, + konj "angle, corner, confined place" (variants xong "corner, angle," Tabari kânj, Kurd. kunj, Hamadâni kom), maybe from the PIE base *g(e)neu-, as above, and related to Mod.Pers. zânu "knee" (Av. žnu-), Skt. kona- "angle, corner," Gk. gony, gonia, L. cuneus "a wedge," Albanian (Gheg dialect) kân "angle, corner," Albanian (Toks) kënd "angle, corner."
Fr.: fonctions orthogonales
A set of functions, any two of which, by analogy to orthogonal vectors, vanish if their product is summed by integration over a specified interval.
Fr.: droites orthogonales
Fr.: trajectoire orthogonale
Math.: An → isogonal trajectory where the family of curves are cut at right angles.
Fr.: vecteurs orthogonaux
Two non-zero vectors which are perpendicular, i.e. their → scalar product is zero.
1) The property of → orthogonal functions.
Molecular hydrogen in which the nuclei (protons) of the two hydrogen atoms contained in the molecule have spins in the same direction. → parahydrogen