Posted by Davin Flateau on 21 Feb 2006 at 5:22 pm.
Filed under General, Astronomy.
In the previous post, I talked about astronomers figuring out the cause of the extragalactic glow of x-rays. But in a separate discovery, astronomers have discovered what’s causing the glow of x-rays observed from within our galaxy. It’s not black holes this time, but huge numbers of white dwarfs, another fate of dying stars. Another source is the hot outer atmospheres of the billions of ordinary stars in our galaxy, including our own sun.
Sky and Telescope has the skinny:
Thanks to NASA’s Rossi X-ray Timing Explorer (RXTE) satellite, astronomers appear to have solved the long-standing mystery of what produces the diffuse glow of X-ray emission that permeates our galaxy. To the surprise of many, the background glow originates from huge numbers of white dwarfs — the dead cores of roughly solar-mass stars — and the hot outer atmospheres (coronae) of ordinary stars.
The Milky Way’s X-ray background was discovered in balloon-borne and satellite experiments in the 1970s. The X-ray emission is smoothly distributed in the galactic plane, with a brightness peak toward the galactic center. Because major X-ray observatories such as Chandra and XMM-Newton were unable to resolve the background into individual objects, many astronomers assumed that the glow came from hot, diffuse interstellar gas.
…
“From the local population of X-ray sources (less than 300 light-years away), we see that most of the sources are accreting white dwarfs or ordinary stars in binary systems,” says Revnivtsev. He and his colleagues propose that approximately a million white dwarfs and a billion normal stars can account for the X-ray background, and that previous Chandra observations had insufficient sensitivity to see them as individual sources.
The funny thing is that the Rossi X-ray Timing Explorer has been in orbit ten years, and was able to scoop newer x-ray observatories like Chandra and XMM-Newton because they really weren’t really designed look at the sky in that specific way. Just because a telescope is old, doesn’t mean you throw it away.
