Binary and Multiple Stars
When you look up at the stars in the night sky they look like individual points of light when in reality most stars belong to binary, trinary, or multiple star systems. What this means is that most stars have other stars in orbit around them much like the planets orbit our Sun. In a binary system you have two stars that orbit around each other. Binary stars come in three types; optical doubles which means from our viewpoint two stars seem next to each other but in reality aren't gravitationally bound. They just lie along the same line of sight. Phyical doubles are two stars that are bound together by gravity. Spectroscopic doubles are so close together that they can only be split using their stellar spectra.
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α Leo (Regulus) in Leo the Lion |
β Cyg in Cygnus the Swan |
ζ Lyr in Lyra the Lyre |
β Sco (Graffias) in Scorpius the Scorpion |
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17 Cyg in Cygnus the Swan. |
95 Her in Hercules the Strong Man. |
δ Cep in Cepheus the King. |
κ Boo in Boötes the Herdsman. |
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Alcor and Mizar (μ UMa) in Ursa Major the Greater Bear (Big Dipper). |
Polaris (α UMi) the North Star in Ursa Minor the Lesser Bear (Little Dipper). |