";s:4:"text";s:2489:" For each star, the other is its companion star.Many stars are part of a system with two or more stars. The brighter star is called the primary star, and the other is the secondary.. Binary stars are important in astrophysics because looking at their orbits allows scientists to find out their masses. The binary star system has a combined apparent magnitude of 2.97, which makes it a full magnitude fainter than Castor A. Binary Star System. For each star, the other is its companion star.Many stars are part of a system with two or more stars. Like its brighter neighbour Sirius in Canis Major, it is one of the nearest star systems to the Sun. A binary star is a star system which is made up of two stars that orbit a common center of mass because of gravitational attraction. A high proportion, perhaps one-half, of all stars in the Milky Way Galaxy are binaries or members of more complex multiple systems. Binary stars are quite common. The brighter and larger star is usually called the primary and the other one the companion star. When two or more stars orbit each other, they are called star systems. Castor Ba, the brighter, larger and more massive component in the system, has 2.98 solar masses and a radius 3.3 times solar. Binary star A binary star [1], often called a double star [2], is a star system in which two stars linked by their mutual gravity orbit around a central point of mass. A binary star is two stars which orbit around each other. Mizar is in fact a four-star system, while Alcor is a binary system in its own right, which means that the entire system consists of six stars, in which a two-star system orbits a four-star system once every 750,000 years or so. Procyon, Alpha Canis Minoris (α CMi), is a binary star system with an apparent magnitude of 0.34, located at a distance of only 11.46 light years from Earth in the constellation Canis Minor. Binary star, pair of stars in orbit around their common center of gravity.