Contact binary star

In astronomy, a contact binary is a binary star system where the stars are so close that they touch each other or have combined to share their atmospheres.  A binary system where the stars share an atmosphere is also called an overcontact binary. The name "contact binary" was invented by astronomer Gerard Kuiper in 1941. Almost every contact binary is an eclipsing binary; eclipsing contact binaries are known as W Ursae Majoris variables, named after W Ursae Majoris.

The stars normally share the same temperatures and masses, as the bigger star normally gives some of its mass and temperature to the smaller star. But sometimes the stars touch physically but keep their same, different temperatures.

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Category:Types of stars