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| Contact binary Image David Darling, The Internet Encyclopedia of Science |
V361 Lyrae is a faint star at the very northernmost edge of the constellation. It can be found less than a degree away from the naked-eye star 16 Lyrae,
V361 us a 5th-magnitude A-type subgiant located around 120.6 ly (37 parsecs) distant. It is an eclipsing binary that does not easily fall into one of the traditional classes, with features of Beta Lyrae, W Ursae Majoris, and cataclysmic variables.
It may be a representative of a very brief phase in which the system is transitioning into a contact binary.
Wikipedia
Contact binaries
Contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes.
A binary system whose stars share an envelope may also be called an overcontact binary.
Almost all known contact binary systems are eclipsing binaries; eclipsing contact binaries are known as W Ursae Majoris variables, after their type star, W Ursae Majoris.
Contact binaries are sometimes confused with common envelopes. However, whereas the configuration of two touching stars in a contact binary has a typical lifetime of millions to billions of years, the common envelope is a dynamically unstable phase in binary evolution that either expels the stellar envelope or merges the binary in a timescale of months to years.
Wikipedia
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