Binary Star - Importance, Visual Binaries, Study Of Orbital Motion, Astrometric Binaries, Spectroscopic Binaries, Eclipsing Binaries - Techniques of observation
stars range bound separations
Binary stars, often called double stars, refer to pairs of stars sufficiently close to each other in space to be gravitationally bound together. Following the laws of gravitation, each of the components revolves around the common center of mass of the system. At least 50% of stars are found to exist as binary systems, according to conservative statistics. There seems to be no obvious preference for particular combinations of brightness, size, or mass differences and a wide range in periods of revolution from less than a day to thousands of years. Likewise, there is a large range in separations from those stars in contact to those separated by thousands of times the Earth to Sun distance. Historically, visual binaries, those that appear as double stars when seen through a telescope, were discovered to be gravitationally bound by William Herschel around 1800.
There are a number of telescopic techniques used to discover and study binary stars. No one telescopic method can be used because of the wide range in the separations exhibited in the systems. The desired information about the orbital motion and the physical quantities of the stars themselves must come from different ways of observing. Hence, there are descriptive classifications of binary stars as determined by the various modes of study discussed below.
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The importance of binaries lies in a number of areas: 1) The analysis of a visual binary (where the two
An x-ray image of the x-ray binary star system LMC X-1 in the Large Magellanic Cloud (LMC). LMC X-1 is seen as the two bright objects at center left and center right. The Tarantula Nebula is at the top of the cloud at left. The picture was taken by the ROSAT x-ray astronomy satellite. ROS…
The first goal generally is to determine the period of revolution, then when feasible, the geometric elements (relating the apparent orbit on the plane of the sky to that on the true plane of the orbit) and the dynamical orbital elements of the system as far as possible, which will lead to the physical characteristics of the stellar components. The simple laws which govern the dynamics of orbital …
Spectroscopic binaries are pairs which are too close to each other as seen from the earth to be resolved into two stars. However, when the light from the star is analyzed with a spectrograph, which spreads the light into a continuous spectrum of colors with dark absorption lines superimposed, the spectral lines are alternately shortened or lengthened indicating Doppler motion, a to-andfro motion a…
X-ray binaries are discovered through space telescopes, which focus on very short-wave energy radiation sources. The International Explorer and the Einstein X-Ray Observatory and other satellites have been used. Some semi-detached pairs emit x–rays provided by mass transfer in a common atmospheric envelope. Close pairs with one component, a neutron star or a black hole, are likely indicated…
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