Astronomers report having observed a rare celestial event- a star being ripped apart by a supermassive black hole.

The rare event- so rare it only happens once every 10,000 years per galaxy, was actually observed back in 2006 but astronomers only realized what they were looking at now when they were analyzing the data.

The international team of astronomers, including Sydney University astrophysicist Sean Farrell, has spent the last three years analyzing archival footage taken by the European Space Agency's X-ray telescope in the hope of spotting a rare object or event.

Spot one they did in the picture of a star being torn apart by a black hole in a galaxy 500 million light years away. The image showed a bright flare- a sign that the star is getting sucked into the black hole. Astronomers were able to observe the star in the next few years with the star getting increasingly brighter until February this year, when the team couldn't find a trace of the star. It had already been swallowed by a supermassive black hole.

''We've been pretty lucky,'' Dr Farrell said. ''We had indeed stumbled on to a very rare extreme event ... we were very lucky that the telescope happened to have this event in its field of view.''

The X-ray telescope was able to pick out the evidence of the destruction in the form of swirling debris which emitted x-rays. The astronomers were also able to measure the temperature of the black hole, which revealed its' mass.

The discovery will be published in an upcoming edition of Astrophysics Journal. The find is important because there is little known about supermassive black holes. Learning more about them could unlock the mysteries of forming galaxies.

''This is very important as their influence on galaxies has an enormous effect on gas, stars, planets and, of course, life itself," Dr Farrell said.

"By studying the boundaries of black holes we can gain crucial knowledge about these extreme objects and their impact in the universe."