An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

→ beta particle.

→ beta particle; → minus; → decay.

An → electron or a → positron emitted from an unstable nucleus during a → radioactive process known as → beta decay.

The term "beta particle" relates to the early history of the → radioactivity studies when the nature of the emergent particles was not elucidated; → particle.

The second brightest star, with an apparent magnitude of 3.86, in the southern constellation → Pictor. Beta Pic is a young star of spectral type A lying 63 → light-years away. It has a luminosity 8.6 times that of the Sun and its surface temperature is 8250 K. Beta Pic is surrounded by a dust and gas disk stretching 400 A.U. away from the star in each direction, 10 times the average distance of Pluto from the Sun. The disk is not symmetric, one side is brighter than the other. Moreover, it has an inner clear zone about the size of our solar system (some 30 A.U.). Recently a probable giant → exoplanet lying in the disk has been imaged.

Beta (β), the second letter of the Gk. alphabet; → Pictor.

→ beta particle.

→ beta particle; → plus; → decay.

A solid object with a mass about 10^-18-10^-15 kg in → interplanetary space that moves in hyperbolic orbit as a result of the solar → radiation pressure.

→ meteoroid.

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 (M_sun). Neilson & Lester (2011, arXiv:1109.4562) recently proposed a mass of 11.6 (+5.0, -3.9) M_sun for Betelgeuse, while Dolan et al. (2008, BAPS 53, APR.S8.6) obtained about 21 M_sun. 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' (ابط‌الجوزاء) "the armpit of Jauza'," from ibt "armpit" + Jauza' "Orion."

Ebtoljowzâ, from Ar. Ibt al-Jauza'.

A unit of energy equal to 10⁴⁴ → joules or 10⁵¹ → ergs, corresponding to the amount of energy liberated in a typical → supernova explosion. It is used by some theoreticians.

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.

An → ansatz initially used to deal with → antiferromagnetism in a quantum system. It has been generalized to various quantum → n-body problems.

First introduced by Hans Bethe (1906-2005), → bethe; → ansatz.

Same as → blue horizontal branch star.

→ 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.

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.

Luigi Bianchi (1856-1928), Italian mathematician; → cosmological; → model.

1) General: Leaning of the mind toward or away from something; especially: a personal and sometimes unreasoned judgment.
Statistics: A → systematic error introduced by selecting items from a wrong population, favoring some of the elements of a population, or poorly phrasing questions.
2) Electronics: A → voltage applied to a device to establish a reference level for operation. Same as initial voltage, initial tension (Ger. die Vorspannung). In a → CCD detector, electronic → offset which prevents negative signal.
3a) General: To give a settled and often prejudiced outlook to.
3b) Electronics: To apply a small voltage to a device to control its operation. See also: → bias error, → bias frame, → bias offset, → bias voltage, → biased, → biased estimate, → biased galaxy formation, → biased sample, → biased statistics, → debias, → kinematic bias, → Lutz-Kelker bias, → Malmquist bias, → observational bias, → sampling bias, → unbiased, → unbiased estimator.

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".
Pištaneš, only in the electronic sense, from piš, → pre- + taneš, → tension.
Varak dâdan, from varak + dâdan "to give," → datum.

A measurement error that remains constant in magnitude for all observations; for example an incorrectly set zero adjustment.

→ bias; → error.

CCD frame with exposure time set to zero and giving the bias level.

→ bias; → frame.

Nurdâd, → exposure; varak→ bias

In → CCD detectors, same as → bias and → offset.

→ bias; → offset.

A voltage applied or developed between two electrodes as a bias.

→ bias; → voltage.

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."

Of a population parameter, if the mean or expectation of the statistics is not equal to the parameter.

→ biased; → estimate.

barâvard, → estimate; varakdâr→ biased.

The theory that bright galaxies form preferentially from anomalously overdense perturbations in the → early Universe.

→ biased; → galaxy; → formation.

A sample that is not a true representative of a → statistical population to which generalizations are to be made. A sample which is not → randomly constituted.

→ biased; → sample.