Betelgeuse

Betelgeuse (α Ori / α Orionis / Alpha Orionis) is the second brightest star in the constellation Orion and the tenth brightest star in the nighttime sky. Although it has the Bayer designation "alpha", it is not as bright as Rigel (Beta Orionis).

Related Topics:
Alpha - Constellation - Orion - Brightest star - Bayer designation - Rigel

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Betelgeuse is a vertex of the Winter Triangle.

Related Topics:
Vertex - Winter Triangle

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Betelgeuse is a red supergiant star, one of the physically largest stars known. If it was placed at the center of our Solar System, the Earth would be engulfed and would be inside it. Its proximity to Earth combined with its enormous size make it the star with the third largest angular diameter as viewed from Earth http://iapetus.phy.umist.ac.uk/rdor/rdor.html, smaller only than the Sun and R Doradus, and one of only a dozen or so stars that telescopes can image as a visible disk as of 2005. (See photo, at right and a picture of hotspots on Betelgeuse). The angular diameter of Betelgeuse was first measured in 1920-1921 by Michelson and Pease using an interferometer on the Mount Wilson 100-inch telescope.

Related Topics:
Red supergiant - Star - Solar System - Angular diameter - R Doradus - As of 2005 - Michelson - Pease - Interferometer - Mount Wilson

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Because Rigel is a blue star and Betelgeuse is a red star, Betelgeuse is actually brighter than Rigel at infrared wavelengths, but not at visual wavelengths.

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