What can you tell me about the supergiant Betelegeuse?
The red supergiant Betelgeuse is one of the largest (in physical size, not
mass) stars known. It is found in the constellation Orion; its `official'
designation is "alpha Orionis". Its mass is about 18 times that of the Sun,
and it is about 520 light years away. The name "Betelgeuse" comes from the
Arabic for "shoulder of the giant". It is a truly enormous star, having a
diameter 500 to perhaps 750 times that of the Sun. If the Sun were replaced
by Betelgeuse, it would extend past the asteroid belt!
The angular diameter of Betelgeuse was measured by Hanbury Brown using
intensity interferometry. The other input is the true physical size of the
star which can be computed from the spectral features.
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Update: June 2012