Older sources suggest that name comes from the Arabic ibt al jauzah, meaning 'armpit of the central one', though the more favoured modern interpretation is from yad al-Jauzā, the 'hand of Orion'. It is particular
bright and prominent star (the tenth
brightest in the sky) and shines with a
red-orange light. With Bellatrix, it forms the shoulders of
Orion the Hunter.
The mottled surface of Betelgeuse, a vast and ancient star approaching the end of its long life cycle.
Betelgeuse is a truly immense star. It is in fact one of the largest stars known, with a
diameter some six hundred times that of the
Sun. This diameter is not fixed: the matter in
Betelgeuse's outer shells swells and contracts by up to a quarter of its volume, over an irregular period of about five years.
This factor is reflected in its shifting
magnitude when viewed from
Earth. Patterns of 'starspots' have also been detected on Betelgeuse's surface.
Betelgeuse is a star in the last stages of its life. It has evolved to the point where
its raw material for nuclear fusion has almost been exhausted, and it is approaching the point - a matter of just a few
million years from now - where a supernova will occur.