Flag falls short as new star is born
IT IS hundreds of light years away, but its discovery challenges the accuracy of Australia's flag.
Astronomers have spotted a previously unknown star that appears to be orbiting Beta Crucis, the lefthand star on the Southern Cross, as viewed on the flag.
The discovery was made by American scientists who turned NASA's Chandra X-ray space telescope towards Beta Crucis. To their surprise they saw two X-ray glows where there should have been only one. The second object turned out to be another star, seemingly circling Beta Crucis every 2000 years.
Nick Lomb, the astronomer at the Powerhouse Museum's Sydney Observatory, said yesterday the smaller companion had never been noticed before because it was lost in Beta Crucis's glare.
"It would be like looking for a glow worm next to a floodlight," said Dr Lomb.
Although 400 times further apart than the Earth is from the sun, from 352 light years away the apparent separation between the two stars is like looking at a pair of car headlights from 100 kilometres away.
Dr Lomb warned that making the flag's Southern Cross scientifically accurate by adding a sixth star would be complicated by the fact that the constellation already has at least two other ignored companions.
Alpha Crucis, or Acrux, the star at the bottom of the flag, has a cosmic partner invisible to the naked eye. And even before the latest discovery, Beta Crucis was known to have its own circling partner, meaning it is really a cluster of three stars.
Showing all eight Southern Cross stars to scale on the flag might be a problem, said Dr Lomb. "The flag would have to be huge, probably the size of Sydney."
Anyway, the astronomer noted, the flag's Southern Cross is only a fleeting stellar feature. Three of its stars, hot giants, are doomed to burn out in a few million years.
And "the shape of the cross is changing as all five stars are moving in very different, random motions. In 20,000 years the difference will be quite noticeable."