December 12, 2012
Astronomers Find Microquasar Outside Our Galaxy
Lee Rannals for redOrbit.com - Your Universe Online
In a microquasar, a black hole with a mass several times that of the Sun pulls material from its companion star into a rapidly-rotating disk. The disk surrounding the black hole can become so hot it emits X-rays. It also propels narrow jets of subatomic particles outward at speeds nearing that of light.
As the "feeding rate" of the black hole varies, the levels of X-ray and radio emission hangs, which is an interplay whose details are not yet fully understood.
"This is, we think, the same mechanism at work in quasars at the cores of galaxies, where the black holes are millions of times more massive. However, in the smaller systems, things happen much more rapidly, giving us more data to help understand the physics at work," said Matthew Middleton, of the University of Durham in the UK and the Astronomical Institute Anton Pannekoek.
He said that understanding how these work is important because astronomers believe quasars play a big role in redistributing matter and energy when the Universe was very young.
Astronomers discovered the first microquasar in 1994, and since then several others have been found, all within our own Milky Way galaxy.
"Obscuration within our Galaxy makes it difficult to study the disks of these microquasars in the Milky Way, but finding one in a neighboring galaxy means we probably can find many more, thus helping our efforts to better understand their physics," Middleton said.
Astronomers used the orbiting X-ray observatory XMM-Newton to discover the object, which has been named XMMU J004243.6+412519.
The behavior of XMMU J004243.6+412519 at both X-ray and radio wavelengths closely parallels the behavior of previously discovered microquasars.
The radio observations indicate that the emission from the object is coming from a small region. The Karl G. Jansky Very Large Array (VLA) helped to detect variations in radio brightness over the course of minutes, indicating that the region is no larger than the distance between the Sun and Jupiter.
"All these indications show that what we have found is, indeed a microquasar," Middleton said .
The team believes that the black hole probably is about ten times more massive than the Sun, and that its companion is a middle-sized star.