Betelgeuse (α Orionis)
The → red supergiant that is the second brightest star in the constellation → Orion. Betelgeuse is one of the biggest stars known with a size of almost 1,000 times larger than the Sun, corresponding to an angular diameter of 43.76 ± 0.12 milli-arcseconds (Perrin et al. 2004, A&A 418, 675). It is a → semiregular variable whose → apparent visual magnitude varies between 0.2 and 1.2 shining very rarely more brightly than its neighbor → Rigel. The energy released by Betelgeuse is estimated to be only 13% in the form of visible light, with most of its radiation being at → infrared wavelengths. The distance of Betelgeuse is 643±146 → light-years (Harper et al. 2008, AJ 135, 1430), while its luminosity is about 140,000 times that of the Sun (→ solar luminosity). Its → spectral type is M2 Iab, its → surface temperature about 3,600 K, and its → initial mass 10 to 20 → solar masses (Msun). Neilson & Lester (2011, arXiv:1109.4562) recently proposed a mass of 11.6 (+5.0, -3.9) Msun for Betelgeuse, while Dolan et al. (2008, BAPS 53, APR.S8.6) obtained about 21 Msun. Its → rotation period is estimated to be about 17 years (Uittenbroek et al. 1998, AJ 116, 2501). Recent observations with the → Very Large Telescope resolve not only the apparent surface of Betelgeuse, but also reveal a large and previously unknown plume of gas extending into space from the surface of the star (Kervella et al. 2009, A&A 504, 115). The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune. This detection suggests that the whole outer shell of Betelgeuse is not shedding matter evenly in all directions. More recently, an image of the surface of the star was obtained using long → baseline → interferometry at infrared wavelengths (Haubois et al. 2009, A&A 508, 923). It shows the presence of an irregular flux distribution possibly caused by enormous → convective cells. A very large dusty envelope has also been observed at larger distances from the star (Kervella et al. 2011, A&A 531, A117).
Betelgeuse, from Ar. Ibt al-Jauza' (
Ebtoljowzâ, from Ar. Ibt al-Jauza'.
In honor of Hans Bethe (1906-2005), Nobel Prize in Physics (1967), for his work on the theory of stellar nucleosynthesis. The unit name was proposed by Steven Weinberg (1933-) in 2006 for Bethe's contributions to the supernova research aftre 1980.
Fr.: ansatz de Bethe
Fr.: étoile BHB
Same as → blue horizontal branch star.
Prefix denoting "two, both, twice."
From L. bi-, cognate of Gk. di-, O.E. twi-; cf. Av. bi- "two," biš "twice," Mod.Pers. do "two," PIE *dwo- "two."
Do, Mid.Pers. do, Av. dva-, Skt. dvi-, Gk. duo, L. duo, E. two, Ger. zwei, Fr. deux.
Bianchi cosmological model
model-e keyhânšenâxti-ye Bianchi
Fr.: modèle cosmologique de Bianchi
A cosmological model based on the theory of → general relativity, which is homogeneous but → anisotropic. There are actually ten dinstinct Bianchi types, classified according to the particular kinds of symmetry they posses.
1) varak; 2) pištaneš; 3) varak dâdan
Fr.: 1, 2) biais; 3) biaiser
Leaning of the mind toward or away from something; especially:
a personal and sometimes unreasoned judgment.
From M.Fr. biais "slant," perhaps ultimately from Gk. epikarsios "slanting, oblique," from epi- "upon" + karsios "oblique."
Varak, from var "side, direction"
+ -ak suffix denoting relation, affinity, similarity
(as in dastak, poštak, pašmak, xarak,
nâxonak, mušak, eynak).
Note also var in yekvar "slanting, inclined".
irang-e varak, xatâ-ye ~
Fr.: erreur de biais
A measurement error that remains constant in magnitude for all observations; for example an incorrectly set zero adjustment.
nurdâd barây-e varak
Fr.: pose pour biais
CCD frame with exposure time set to zero and giving the bias level.
Fr.: voltage de biais
A voltage applied or developed between two electrodes as a bias.
Marked by or exhibiting bias; characterized by settled and often prejudiced outlook.
Biased, from → bias + adj. suffix -ed.
Varakdâr, from varak, → bias + -dâr "possessing, having," from dâštan "to possess, to have."
Fr.: estimation biasiée
Of a population parameter, if the mean or expectation of the statistics is not equal to the parameter.
biased galaxy formation
diseš-e varakdâr-e kahkašânhâ
Fr.: formation biaisée de galaxies
The theory that bright galaxies form preferentially from anomalously overdense perturbations in the → early Universe.
Fr.: échantillon biaisé
Fr.: statistique biasée
A statistics based on a → biased sample.
Fr.: cristal biaxe
A birefrigent crystal, such as mica, that is characterized by having two optical axes along which light is propagated with equal velocities.
A → microwave → polarimeter designed specifically to target the → B-mode signature of → inflation in the → cosmic microwave background polarization. BICEP2 observed from the South Pole for three seasons from 2010 to 2012. This 26 cm aperture → telescope comprised an all-cold refracting optical system equipped with a → bolometer array of 512 → detectors (256 pixels) operating at 150 GHz.
BICEP2, the upgraded version of the first BICEP, short for Background Imaging of Cosmic Extragalactic Polarization.
Fr.: lentille biconcave
Describing a lens with two concave faces.
Fr.: lentille biconvexe
A → spherical lens with two convex faces. The radii of curvature for the two surfaces may or may not be the same.