Betelgeuse (pronounce /ˈbiːtəldʒuːz/ or /ˈbɛtəldʒuːz/) (Alpha (α) Orionis) is a semiregular variable star located 427 light-years away from Earth. It is the second brightest star in the constellation Orion and the ninth brightest star in the night sky. Although Betelgeuse has the Bayer designation alpha, Rigel (Beta Orionis) is brighter. The star is a vertex of the Winter Triangle asterism. Astronomers believe Betelgeuse is only a few million years old but has evolved rapidly because of its huge size.