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W Ursae Majoris star

W Ursae Majoris
W Ursae Majoris
Photo: ESO Online Digitized Sky Survey

A type of eclipsing binary with a very short period of a few hours up to a day. In W UMa systems, the component stars, which are of spectral type F or G and lie on or near the main sequence, form a contact binary and have pulled each other into teardrop shapes. The primary and secondary minima are virtually the same (some 0.6 to 0.8 magnitude deep) and there is a continuous light variation throughout the orbit, with no clear start or end to an eclipse.

W Ursae Majoris itself lies 162 light-years away and consists of two stars not unlike the Sun, the primary with a mass of 0.99 Msun, a radius of 1.14 Rsun, and a luminosity of 1.45 Lsun, and the secondary with a mass of 0.62 Msun, a radius of 0.83 Rsun, and a solar-equivalent luminosity.

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   • variable stars

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