Black Hole Missing a Galaxy |
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Written by spacetravel.org
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Saturday, 17 September 2005 21:28 |
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Astronomers have found a quasar, a massive black hole, but no evidence of a surrounding galaxy. An international team of astronomers, using images from the Hubble Space Telescope and spectroscopy from the Very Large Telescope in northern Chile, selected 20 quasars, in order to study the properties of their host galaxies. They found galaxies encircling 19 of them. However, they found no sign of a galaxy around HE0450-2958, a quasar located about 5 billion light-years away. Instead, they found a cloud of ionised gas about 2,500 light-years in size near the quasar.
Quasars are the most radiant objects in the Universe. They are only about the size of the Solar System, but can emit up to 100 times as much radiation as a whole galaxy. In order to maintain their brightness, quasars must feed off the galaxies in which they reside. The astronomers believe that HE0450-2958 is being fed by its surrounding gas cloud, and that this is enabling to become a quasar. They estimate that the quasar is siphoning off about one Suns worth of mass from the gas cloud every year.
The researchers also found a deeply distorted companion galaxy, 50,000 light-years away from the quasar. It is brighter in the infrared spectrum than most galaxies, and it is creating new starts at a very rapid rate. The researches believe that this galaxy may have experienced a collision about 100 million years ago, possibly with the quasar. Such a collision would have stirred up gas and dust, enhancing star formation. Heat from young stars, and from gas and dust warmed by the collision, may have caused the galaxys infrared glow.
The researchers think that either the quasar is encircled by a galaxy that is too small or too faint to be detected, the collision with the companion galaxy may have somehow caused the quasars galaxy to disappear, the gas cloud could be gas stolen by a slow-moving black hole as it travelled through the disc of a spiral galaxy, or the quasar is encircled by a galaxy made up almost entirely of dark matter.
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