Binary
Binary or ductile is a star system in which two stars revolve around a common mass center. The brightest star in the star system is called the principal, and other stars darker than the star are called symmetry, reflection, or mating. However, when referring to a dark star, bright stars may be referred to as reflection, reflection, or pairing. According to recent research, a large number of stars belong to the multicellular system. Binary systems are very important in astrophysics because their mutual orbits can be seen in their masses. The mass of individual stars can be determined by estimation from the binary. Binary is different from optical 'duality', duality appears close to each other when viewed from the earth, and may not be bound by gravity. Binary pairs can be optically separated and indirect methods such as spectroscopy can be used. When the twin revolves around the orbit including the direction of the line of sight, they cause an eclipse, which is called ecliptic.