New star found in Southern Cross

Stephen Withers
Thursday, 08 February 2007 04:38

Science - Space

It's taken a month to hit the news, but astronomers have discovered that Beta Crucis - the left point of the Southern Cross - has a binary companion.

The discovery revealed in early January by a team from Swarthmore College and West Chester University of Pennsylvania, led by Professor David Cohen. The team was studying x-ray emissions from the star using the orbiting Chandra X-Ray Observatory, and detected a second nearby source.

The separation of the two stars as seen from the telescope is said to be equivalent to that of the headlights of a car about 100km away - "well within the capabilities of NASA's Chandra X-ray Observatory."

The companion star has not been detected by optical telescopes because it is so much dimmer than Beta Crucis, which is the nineteenth brightest star in the sky. Extending the previous analogy, it is as if one of the headlights was replaced by a firefly. Since the x-ray brightness of the two starts is much more similar, Chandra could show them both.

It has yet to be determined whether or not the two stars are orbiting each other, or if they just happen to passing close to each other at the moment. In this context, 'close' is approximately ten times the distance between our Sun and Pluto, and we see the stars as they were 352 years ago.

The researchers note that if the newly discovered star was added to the Australian flag, it would not be distinguishable from Beta Crucis.