A binary star system is a star system with two or more stars orbiting around each other. Number of stars in each system are from 2 to 7 as classified yet.
With the help of these binary stars which are very important in the field of astronomy, we can estimate the mass of the partner star in the binary system. Estimating mass is useful for contrasting it against the temperature and apparent luminosity, helping us determine absolute luminosity and distance.
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| Eclipsing Binary |
There are many categories of binary star system, classified by their visual properties as observed/view from earth or a satellite.These including eclipsing binaries, visual binaries, spectroscopic binaries and astrometric binaries.
Eclipsing binary stars are those whose orbits form a horizontal line from the point of observation; essentially, what the viewer sees is a double eclipse along a single plane; Algol for example.
A visual binary system is a system in which two separate stars are visible through a telescope that has an appropriate resolving power. These can be difficult to detect if one of the stars’ brightness is much greater, in effect blotting out the second star.
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| Spectroscopic Binary |
Spectroscopic binary stars are those systems in which the stars are very close and orbiting very quickly. These systems are determined by the presence of spectral lines – lines of color that are anomalies in an otherwise continuous spectrum and are one of the only ways of determining whether a second star is present. It is possible for a binary star system to be both a visual and a spectroscopic binary if the stars are far enough apart and the telescope being used is of a high enough resolution.
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| Astrometric Binary |
Astrometric binary stars are systems in which only one star can be observed, and the other’s presence is inferred by the noticeable wobble of the first star. This wobble happens as a result of the smaller star’s slight gravitational influence on the larger star.
With the help of these binary stars which are very important in the field of astronomy, we can estimate the mass of the partner star in the binary system. Estimating mass is useful for contrasting it against the temperature and apparent luminosity, helping us determine absolute luminosity and distance. 
A visual binary system is a system in which two separate stars are visible through a telescope that has an appropriate resolving power. These can be difficult to detect if one of the stars’ brightness is much greater, in effect blotting out the second star.
