The Heart of the Scorpion

The red supergiant Antares, fiery heart of Scorpio the Scorpion, blazes low in the south-east. Ten thousand times brighter than the Sun, hundreds of times larger, Antares is dying.

All stars are fueled by nuclear fires, converting hydrogen into helium. The hydrogen fuel in the core of Antares has been used up.

The outer layers of the star have now ignited. As they heat up, they expand. The star's heat is spread over a huge area. The surface of Antares, the part we actually see, is cool -- and red.

The nuclear fires will continue for a while, but that only puts off the inevitable. Soon, now, Antares will die.

The outward pressure of the nuclear fire has kept gravity at bay for millions of years. Now, as this fire flickers and dies, gravity will take over. Antares will contract until it becomes a compact ball of neutrons only about as big as Burlington -- a neutron star. Or it may wink out of sight altogether as a black hole.

We can't see neutron stars or black holes. But a circling companion star may leak gasses onto its partner. More than half the stars in the sky do have such companions. As the gasses approach at greater and greater speeds, they heat up, and produce X-rays. One day we will "see" an X-ray source where Antares is now. Because Antares has a companion.

(06/04/08)