Astronomers discover galaxy's hottest star

A TEAM of British astronomers has discovered the hottest star in the galaxy. With a surface temperature of 170,000 degrees, it glows 30 times hotter than our own sun. About 600 light years away in the constellation of Draco the Dragon, the star is a white dwarf with the unromantic name of RE1502+66.

It is at such a high temperature that it glows hotter than white hot, radiating at wavelengths 30 times shorter than the visible part of the spectrum. Professor Ken Pounds, of the University of Leicester, one of the leaders of the team that found the star, said: 'It is a faint and relatively insignificant object optically and you'd need a big professional telescope to see it.'

The star showed up on a survey of the sky at the extreme ultraviolet end of the spectrum. Using the UK Wide Field Camera on board the Rosat satellite, Professor Pounds and his colleagues have catalogued 384 objects radiating in the extreme ultraviolet. In ultraviolet, RE1502+66 'shows up incredibly bright and shines out because it is so hot'.

Even so, astronomers can pick up radiation from the star and the others in the catalogue only because the sun and the solar system sit inside a 'hot bubble' of rarefied hydrogen gas which does not obscure as much of the radiation as the colder denser gas of the normal interstellar medium.

Professor Pounds believes that the information from Rosat will allow astronomers to map out the 'superbubble' in three-dimensions and 'that might be one of the most important things that comes out of the data'.