In the Universe there are an immense number of star systems, however not all of them are like our Solar System; In fact, a large majority of all existing stars do not make up a single star system like our sun (that is, with a single central star), but rather make up double, triple or multiple star systems, which They revolve around a common center of gravity. This is how binary systems (two stars) or multiple systems (more than two stars) appear, which together make up the 85% of all the star systems in the Universe, making our Solar System truly a curious exception.
As they condense, many stellar embryos fragment, forming multiple systems of two or more stars that revolve around a common center and remain linked by their mutual gravitational attraction. Some are unstable and end up falling apart.
The most common are double systems: in them, the most massive star is called primary and the smallest is called secondary. Almost half of the stars in our galaxy are part of double systems, which provide various data about their structure.
They allow us - in many cases - to determine their masses, the influence of the attraction of one star on the structure of another, etc., from time to time, one of the stars of the pair is practically invisible, but can be detected by its effects on the orbit of the other. This has given rise to some of the most interesting discoveries of the last decade, such as the study of certain You do not go, which take place during the interaction between a binary system, composed of a red giant and a white dwarf.
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