Betelgeuse

Called Alpha Orionis, or Betelgeuse, it is a red supergiant star marking the shoulder of the winter constellation, Orion the Hunter (see diagram below right). Supergiant stars live life in the fast lane - they exist for a very short period of time (maximum 100 million years), compared to ordinary stars, like our Sun, of 10 billion years. Supergiants are 10 - 500 times the mass of the Sun, and are many thousands of times more luminous (brighter) due to the faster rate at which they consume their nuclear fuel.

The Hubble image reveals a huge ultra-violet atmosphere with a mysterious hot spot on the stellar surface. The enormous bright spot, more than ten times the diameter of Earth, is at least 2,000°C hotter than the surface of the star.

A Giant Among Giants

Betelgeuse is so vast that, if it replaced the Sun at the centre of our Solar System, its outer atmosphere would extend past the orbit of Jupiter, swallowing all the planets from Mercury to Jupiter - including the Earth! (see diagram above). Most supergiants end their lives catastrophically as a supernova. This happens when the fuel in the core runs out, and so cannot withstand the pressure of the stellar material above. Gravity makes it collapse in on itself - causing the explosion. What remains is frequently a neutron star, or often a Black Hole.

The H.S.T. continues to break down the limits of our knowledge about the Universe. For the latest information, see the Space Telescope Science Institute website.

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