What is a double star?
As the view is from the ground, there are a number of pairs of stars that seem very close to each other and are often described as double stars. In some cases, this results from a random alignment of two stars, which are in fact very distant apart - it is known as optical double. Alternatively, the stars can be close enough to interact with gravity to orbit each other - it is known as the binary star system. More star systems with more than two stars orbiting are also possible. It is assumed that up to 85% of the stars in our galaxy are in more star systems, including binary files.
There are many examples of double stars of both types. Zeta Lyra, near the light star Vega, is an example of an optical double star - two stars are distinguished by a telescope. Sirius A and B and Alpha Centauri A and B are examples of binary star systems. Both of these systems appear as the only star with the naked eye.
where it is possible to distinguish the binary system into two separate stars, either by the naked eye or a telescope, the system is known as visual binary. These can generally be distinguished from optical doubles by observing stars in relation to each other. In rare cases, the stars, as the view are from the ground, can eclipse each other, resulting in a periodic reduction in the light of the stars. Algol, in the constellation Perseus, is an example where the dimming that takes place every few days is actually visible to the mere eye. Where eclipses occur, the averages of both stars from the duration of dimming can be calculated.
In many cases, the double star appears as one star, even though it is viewed by a strong telescope, because the stars of the components are very close and/or very distant. There are a number of methods that can be set to determine whether a star is actually a binary system containing two stars. Different types of stellar produce recognizable spectra thanks to their otliby a snap composition. If the emission spectrum analysis of the remote, the light object indicates two different types of stellar spectrum, it would indicate that it is a double star system containing two different types of stars.
Another method of detection of binary stars, again including star spectra, uses Doppler's effect. In a double stellar system, one of the stars moves towards or from the ground because the stars orbit each other. The stars' spectrum will be shifted in blue as it is approaching and moves when it retreats. This situation will be reversed regularly, indicating orbital movement, although only one of the stars can be observed.
double star can be close enough to each other so that the gravity of one star pulls the material from the other. These are known as contact binary files. This situation may occur when one of the stars extends to the point where part of its external material extends into the zone where the gravitational move of the other star is stronger. One such exampleM is a binary star system Beta Lyrae, also known as Sheliak.