Nearby Galaxy Discovery
Astronomers have located an exceptionally massive black hole in orbit around a huge companion star. Intriguing implications for the evolution and ultimate fate of massive stars may result because of this find. The black hole is part of a binary system in m33, a nearby galaxy about 3 million light years from Earth. The mass of the black hole, known as M33X-7 was determined to be 15.7 times that of the Sun when data from NASA’s Chandra X-Ray Observatory and the Gemini Telescope on Mauna Kea, Hawaii were combined.
M33X-7 is the most massive stellar black hole known. A stellar black hole is formed from the collapse of the core of a massive star at the end of its life. “This discovery raises all sorts of questions about how such a big black hole could have been formed, “ said Jerome Orosz of San Diego State University, lead author of the paper appearing in the October 18 issue of the Journal Nature.
M33X-7 orbits a companion star that eclipses the black hole every three and a half days. The companion star also has an unusually large mass, 70 times that of the Sun. This makes it the most massive companion star in a binary system containing a black hole. The properties of the M33X-7 binary system –a massive black hole in a close orbit around a massive companion star—are difficult to explain using conventional modules for the evolution of massive stars. The parent star for the black hole must have had a mass greater than the existing companion in order to have formed a black hole before the companion star.
The massive star would have a radius larger than the present separation between the stars, so the stars must have had a radius larger than the present separation between the stars. The stars must have been brought closer while sharing a common outer atmosphere. This process typically results in a large amount of mass being lost from the system, so much that the parent star should not have been able to form a 15.7 solar-mass black hole.
This entry was posted on Saturday, November 10th, 2007 at 8:34 pm 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.
