double star


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Related to double star: Optical double star

binary star

binary star or binary system, pair of stars that are held together by their mutual gravitational attraction and revolve about their common center of mass. In 1650 Riccioli made the first binary system discovery, that of the middle star in the Big Dipper's handle, Zeta Urase Majoris. True binary stars are distinct from optical doubles—pairs of stars that lie nearly along the same line of sight from the earth but are not physically associated. Binary stars are grouped into three classes. A visual binary is a pair of stars that can be seen by direct telescopic observation to be a distinct pair with shared motion. A spectroscopic binary cannot be seen as two separate stars, even with the most powerful telescopes, but spectral lines from the pair show a periodic Doppler effect that indicates mutual revolution. Some lines indicate motion toward the earth while others indicate motion away; later, as the stars revolve around in their orbit, this pattern reverses. An eclipsing binary has the plane of its orbit lying near the line of sight, and shows a periodic fluctuation in brightness as one star passes in front of the other. The more massive star (A) of a binary is called the primary, and the less massive (B) is called the secondary; e.g., Sirius A and Sirius B are the primary and secondary components of the Sirius system. It seems likely that more than two-thirds of the stars in our galaxy are binary or multiple (a system of more than two stars moving around their mutual center of mass), since many stars within 30 light-years of the sun are binary or multiple. The masses of the components of a spectroscopic binary can be determined from the observed motions and Newton's law of gravitation; binary stars are the only stars outside the solar system for which masses have been directly determined. Binary stars are thus important indicators from which the masses of all similar stars can be deduced. Measurements of the masses of some of the visual binary stars have been used to verify the mass-luminosity relation. Although most binary stars have distance between them, the components of W Ursae Majoris binaries are actually in contact with each other, their mutual gravity distorting their shapes into teardrops. There are binary systems in which one member is a pulsar: PSR 1913+16, for example, has an orbital period of 7 hr 45 min; in this case the other star is also a neutron star. The orbital period decreases as the system loses energy in the form of gravitational waves; used as a clock to measure the effect of the curvature of space-time on the binary's orbit, such a system confirms Einstein's theory of general relativity.

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double star

A pair of stars that appear close together in the sky. There are two types: optical double stars and physical double stars. Stars in an optical double, such as Deneb, appear close only because they happen to lie in very nearly the same direction from Earth; they are actually too far apart to be members of a dynamically linked system. Stars in a physical double are sufficiently close together for their motions to be affected by their mutual gravitational attraction. They are more usually known as visual binaries.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

double star

[¦dəb·əl ′stär]
(astronomy)
A star which appears as a single point of light to the eye but which can be resolved into two points by a telescope.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Look for the 7.3-magnitude primary of double star STF 131 in the northwest region of the cluster.
Journal of Double Star Observations, Spring 2008, , 3(2),p.59-65.
Additional Clusters and Double Stars in and near Auriga Object RA Dec.
The Washington Double Star Catalogue lists the star as having 2 components, with magnitudes of 7.4 and 7.9 at a separation of 0.36 arcseconds (epoch 2011.8).
This difference in speed could imply that VFTS 102 is a runaway star -- a star that has been ejected from a double star system after its companion exploded as a supernova.
We now know that this pair is not a true double star, but an optical double.
This one is a wide double star with enough difference in brightness between its components (magnitudes 2.5 and 8.7) to play a neat trick on your eye.
On Tuesday, the banks decided not to accept Double Star's demand that they slash the sales price by 16.2 percent to 800 billion won ($710 million).
The Johannesburg Centre of ASSA is in the process of renovating the cardex archive of double star measurements going back to 1835.
Given that three of the first five home all raced close to the pace, that was probably a better effort from Double Star than it appeared at first glance.
Washington, Dec 8 (ANI): Best visuals of a double star system have been captured for the first time, in which the cooler and larger of the two has lost most of its material to its 'vampire' companion, a new study has revealed.