Chandra Telescope Detects Light Echo
From the very center of the Milky Way Galaxy comes evidence of a monumental outburst from the supermassive black hole occupying the center of the galaxy. An x-ray light echo was produced by gas entering the black hole, called Sagittarius A* (pronounced “A- star), and producing x-ray light, which was then reflected by gas clouds near the object. While the principal x-rays arrived at the Earth fifty years ago, the reflected rays arrived via a longer route and got here just in time to be recorded by the Chandra x-ray telescope. Although the outburst occurred before the advent of satellites to witness it, with the aid of Chandra, it has been possible to peer into the past of this destructive force.
Chandra has already been able to observe subsequent outbursts which were much less powerful, but the x-ray echo indicated the blast that produced it was about one thousand times brighter and lasted one thousand times longer that the more recent, directly observed outbursts.
The presence of Sagittarius A* in the center of the galaxy has long been known. Containing a mass equivalent to about three million suns, the black hole is extremely faint at all wavelengths, x-rays in particular, which indicates that stars and gas seldom approach near enough to be engulfed. If another huge outburst had occurred in the last fifty years, evidence would have enabled an x-ray telescope to detect it. It appears that the black hole in the center of our galaxy has fewer opportunities to consume matter than the more active black holes inhabiting the center of many other galaxies.
Researching information about the light echo emanating from Sagittarius A* could help to understand how the black hole feeds–whether it drags in material from the winds of young stars in the vicinity. This involves the black holes being an unstable disk of matter, swirling around the black hole, approaches the edge in clumps, and emitting x-rays as they vanish into the abyss. In addition, information obtained from this study can possibly shed light on the molecular clouds near the galaxy’s center, particularly the dense centers of the clouds where new stars could be in the process of being created.
Alternate theories as to the source of the light echo such as a neutron star or black hole drawing material from a binary companion were countered by variations in the x-ray emissions among three Chandra observations in 2002, 2004, and 2005. This data showed the outburst to be unusually long and bright to have been a binary.
This entry was posted on Tuesday, September 25th, 2007 at 6:34 am and is filed under Public Relations, Space Agency News. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
