Fr.: limite de Oort
1) The upper limit for the density of all matter in the plane of the Galaxy near the Sun's
locality, as calculated from the velocities and distribution of stars
in relation to the gravitational field of the Galactic disk. The value is
0.14 solar masses per cubic parsec, or 9.5 x 10-24 g cm3.
Fr.: minimum de Oort
Fr.: constantes de Oort
Two parameters, denoted A and B, that describe the major features of our Galaxy's differential rotation in the Sun's neighbourhood. A is one-half of the shear and equal to +14.4 ± 1.2 km s-1 kpc-1, and B, one-half of the vorticity, equal to -12.0 ± 2.8 km s-1 pc-1.
1) General: The state or quality of being opaque.
From Fr. opacité, from L. opacitatem (nom. opacitas) "shade, shadiness," from opacus "shaded, dark, opaque."
Kederi, from keder "opaque," from Ar. kader + -i suffix forming nouns from adjectives.
M.E., from M.Fr. opalle, from L. opalus, from Gk. opallios "opal, gem;" probably from a source akin to Skt. upala "jewel, precious stone."
Loan from E., as above.
1) The state of being → opalescent, or
emitting an → iridescence like that of
Exhibiting a play of colors like that of the opal.
Not permitting a radiation to pass through.
Adj. form of → opacity.
O.E. open "not closed down, raised up," also "uncovered, bare; plain, evident," related to up; from P.Gmc. *upana (cf. O.N. opinn, Swed. öppen, Dan. aaben, O.Fris. epen, O.H.G. offan "open"), from PIE *upo "up from under, over;" cf. L. sub; Gk. hypo; O.Pers. upā (prep.) "under, with;" Av. upā, upa (prep.; prevb) "toward, with, on, in;" Mod.Pers. bâ "with," from abâ; Skt. úpa (adv., prevb., prep.) "toward, with, under, on."
Bâz "open," from Mid.Pers. abâz-, apâc-, O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind."
xuše-ye bâz (#)
Fr.: amas ouvert
A loose grouping of dozens or hundreds of young stars distributed in a region a few light-years across. Open clusters are relatively young, typically containing many hot, highly luminous stars. They are located within the disk of the Galaxy, whence their older name Galactic clusters.
Fr.: intervalle ouvert
An interval that does not include its two endpoints.
open magnetic field line
xatt-e bâz-e meydân-e meqnâtisi-ye
Fr.: ligne ouverte de champ magnétique
In the context of solar physics, a → magnetic field line when it crosses the solar surface only once, i.e., when it goes from surface to infinity. This is the case at a sufficiently large scale in → coronal holes. This is mostly not the case in → active regions.
Fr.: ensemble ouvert
fazâ-ye bâz (#)
Fr.: espace ouvert
A space of infinite volume without any boundary. Triangles which lie on the surface of an open space will have a sum of angles which is less than 180°. An open space has a negative → curvature. See also → open Universe, → closed space.
Fr.: système ouvert
giti-ye bâz (#)
Fr.: Univers ouvert
Fr.: FBF ouverte
The capability of being put into use, operation, or practice.
Capable of operating or of being operated.
To function or work; to make something function or work.
From L. operari "to work, labor," L. opus "a work, labor, exertion," Av. *āpah-, *apah- "to do, operate," see below, Skt. ápas- "work, action, religious act;" O.H.G. uoben "to start work, to practice, to honor;" Ger. üben "to exercise, practice;" Du. oefenen; O.E. æfnan "to perform, work, do," afol "power"); PIE base *op- "to work, perform."
Âpâridan, from âpâr-, from Av. *āp(ah)- "to do, operate," as above, + suffix -ar (as in vadar- "weapon," zafar- "jaw," baēvar- "thousand," and so on), shifted to -âr, + -idan suffix of infinitives. The Av. *āpah- "to do, operate," is extant in Mod.Pers. xub "good;" Mid.Pers. hwp, xub "good;" from Av. huuāpah- "doing good work, masterly," from huu-, hv- "good" → eu- + āpah- "work, deed," hauuapanha- "creativity;" cf. Skt. sv-ápas- "doing good work, skillful;" PIE base *op-, as above.