An illustration, top, depicts the catastrophic destruction of a star by a black hole, an event confirmed by observations from two X-ray Observatories: NASA's Chandra, bottom left, and ESA's XMM-Newton, bottom right. (Illustration: NASA/CXC/M.Weiss; X-ray: NASA/CXC/MPE/S.Komossa et al.; Optical: ESO/MPE/S.Komossa.)
Thanks to two orbiting X-ray observatories, astronomers have the first strong
evidence of a supermassive black hole ripping apart a star and consuming a
portion of it.
The event, captured by NASA's Chandra and ESA's XMM-Newton X-ray Observatories,
had long been predicted by theory, but never confirmed.
Astronomers believe a doomed star came too close to a giant black hole after
being thrown off course by a close encounter with another star. As it neared the
enormous gravity of the black hole, the star was stretched by tidal forces until
it was torn apart. This discovery provides crucial information about how these
black holes grow and affect surrounding stars and gas.
"Stars can survive being stretched a small amount, as they are in binary
star systems, but this star was stretched beyond its breaking point," said
Stefanie Komossa of the Max Planck Institute for Extraterrestrial Physics (MPE)
in Germany, leader of the international team of researchers. "This unlucky
star just wandered into the wrong neighborhood."
While other observations have hinted stars are destroyed by black holes (events
known as "stellar tidal disruptions"), these new results are the first
strong evidence. Evidence already exists for supermassive black holes in many
galaxies, but looking for tidal disruptions represents a completely independent
way to search for black holes. Observations like these are urgently needed to
determine how quickly black holes can grow by swallowing neighboring stars.
Observations with Chandra and XMM-Newton, combined with earlier images from the
German Roentgen satellite, detected a powerful X-ray outburst from the center of
the galaxy RXJ1242-11. This outburst, one of the most extreme ever detected in a
galaxy, was caused by gas, heated to millions of degrees Celsius, from the
destroyed star being swallowed by the black hole. The energy liberated in the
process was equivalent to a supernova.
"Now, with all the data in hand, we have the smoking gun proof that this
spectacular event has occurred," said coauthor Guenther Hasinger, also of
MPE.
The black hole in the center of RXJ1242-11 is estimated to have a mass of about
100 million times Earth's sun. By contrast, the destroyed star probably had a
mass about equal to the sun, making it a lopsided battle of gravity. "This
is the ultimate David versus Goliath battle, but here David loses," said
Hasinger.
The astronomers estimated about one percent of the star's mass was ultimately
consumed, or accreted, by the black hole. [...]
Other dramatic flares have been seen from galaxies, but this is the first studied with the high-spatial resolution of Chandra and the high-spectral resolution of XMM-Newton. Both instruments made a critical advance. Chandra showed the RXJ1242-11 event occurred in the center of a galaxy, where the black hole lurks. The XMM-Newton spectrum revealed the fingerprints expected for the surroundings of a black hole, ruling out other possible astronomical explanations.
http://www.nasa.gov/home/hqnews/2004/feb/HQ_04061_black_hole.html
Category: Opinion & Perspective
