W Ursae Majoris stars (or W UMa stars for short) are a type of eclipsing binary star system where the two stars are in physical contact. Each star has its own independent core where fusion reactions take place, however they share one common photosphere. The shape of the combined system is determined by the combined effects of gravity and centrifugal force, leading to a double-lobed shape, as shown in the depictions shown above of (from top to bottom) Epsilon Coronae Australis, 44i Boötis and RW Doradus.
