European astronomers witness destruction of a star by a black hole

Brussels, 20 Feb 2004

An international team of astronomers, led by the Max Planck Institute for extraterrestrial physics (MPE), believes it is the first to see evidence of the destruction and partial consumption of a star by a super massive black hole.

According to data from the European Space Agency's (ESA) XMM-Newton and NASA's Chandra X-ray observatories, the event happened at the centre of a galaxy known as RX J1242-11. The team believes that a star, knocked off course after a close encounter with another star, ventured too close to the giant black hole and was stretched by tidal forces until it was torn apart.

These tidal forces are the same that cause lunar tides on Earth, albeit an extreme example. The black hole in the centre of RX J1242-11 is estimated to have a mass equivalent to 100 million Suns, ensuring that once it passed close, the destroyed star, with a total mass similar to that of the Sun, didn't stand a chance.

'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 MPE's Dr Stefanie Komossa, who led the team. 'This unlucky star just wandered into the wrong neighbourhood.'

What actually allowed the team to observe the event was a powerful X-ray burst, caused when gas from the destroyed star was heated to millions of degrees before being consumed by the black hole. 'Now, with all of the data in hand, we have the smoking gun proof that this spectacular event has occurred,' said Professor Günther Hasinger, also of MPE.

The team estimates that around one hundredth of the mass of the star was swallowed, or accreted, by the black hole. This is consistent with theoretical predictions of such an event, based on calculations of the momentum and energy of the accretion process.

The scientific significance of this discovery relates to the crucial information it provides on how quickly such black holes can grow by swallowing neighbouring stars and gas.

For further information on the XMM-Newton observatory, please visit:
http://www.esa.int/esaSC/120385_index_0_ m.html

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