Binary Stars

Binary Star System
A binary star system is one where two stars orbit
around a central gravitational mass.

Binary Stars

  • our Sun is alone in space, but most star are in group of two or more.
  • binaries are double stars and there are various kinds.
  • true binary stars are two stars that held together by one another gravity.

  • optical binaries are not binaries at all. They are two stars that look as if they are together because they are roughly the same line sight from the earth
  • eclipsing binaries are true binary stars that spin around in exactly the same line of sight from the earth, and keep blocking out each other’s light.
  • spectroscopic binaries are true binary stars that spins so closely together that the only way of knowing that are two stars is by the change in colour.

Measuring in spectroscopic binaries.

  • the star Epsilon, in the constellation of Lyra, is called the Double Double because it is in a pair of binaries.

The Double Double is easy to find as one of bright stars
in the tiny Lyra constellation.

  • Mizar, In ursa Major, was the first binary star to be discovered by telescope in about 1617.

Mizar on the right and its companion, Alcor, form an optical binary.

  • Albireo, in cygnus, is an optical binary that is visible to the naked eye – one star looks gold in colour and the other looks blue.

Not binary, the double star, Albireo – sometimes known as Beta Cygni,
the difference obvious.


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