Astronomers have located an exceptionally massive black hole in
orbit around a huge companion star. This result has intriguing
implications for the evolution and ultimate fate of massive
stars. The black hole is part of a binary system in M33, a
nearby galaxy about 3 million light years from Earth. By
combining data from NASA’s Chandra X-ray Observatory and the
Gemini telescope on Mauna Kea, Hawaii, the mass of the black
hole, known as M33 X-7, was determined to be 15.7 times that of
the Sun. This makes M33 X-7 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
18th issue of the journal Nature. M33 X-7 orbits a companion
star that eclipses the black hole every three and a half days.
The companion star also has an unus