What is a binary star?

What is a binary star?

The term binary star is actually a star system of two stars that orbit around one centre of mass. The brighter star is considered as the primary star, while the dimmer of the two is the secondary. A binary star is often confused with two stars that appear close together to the naked eye from Earth, but in reality are very far apart.

The data collected from binary stars allows astrophysicists to calculate the relative mass of similar single stars as when two stars orbit one another, their mass can be calculated very precisely.

Binary stars categories

Classification based visual properties

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 plan.

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.

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 colour 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.

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.

Binary pairs can be classified based on their orbit

Wide binaries are stars that have orbits which keep them spread apart from one another. These stars evolve separately, with very little impact from their companions. They may have once contained a third star, which booted the distant companion outward while eventually having been ejected themselves.

Close binaries, on the other hand, evolve nearby, able to transfer their mass from one to the other. The primaries of some close binaries consume the material from their companion, sometimes exerting a gravitational force strong enough to pull the smaller star in completely.

Now you have learnt what it is a binary star and it is a great time to name a pair of stars and offer them as Valentine’s gift.




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