Star torn apart by Super Massive Black Hole

5 August 2011

An international team of astronomers have observed an incredibly rare event that occurs once every ten thousand years per galaxy. The astronomers were able to observe a star that had strayed too close to a Super Massive Black Hole being literally torn apart.

Dr Sean Farrell, an ARC Post-Doctoral Fellow in the School of Physics and the Australian representative, said the observation of a star's demise was first made in 2006 through the European Space Agency's X-Ray Telescope, XMM-Newton. The astronomers were researching archival data when they noticed the bright flare, which they realised was the signature of a star being ripped apart in a galaxy 500million light years away.

The star, initially detected in 2006 by Dr Dacheng Lin, who led the study, was observed again in 2007, by which time it had increased in brightness. Dr Lin researched data from 1992, which showed there was no trace on any X-ray source dating back to that time. In February 2011, using NASA's SWIFT X-ray Telescope, Lin observed the area again and found the flare had dimmed significantly.

It was then that the international collaborators knew they had witnessed something truly astonishing. "Dr Lin's research raised the possibility that we had indeed stumbled onto a very rare extreme event," says Farrell. "We were very lucky that the telescope happened to have this event in its field of view. Of course when we realised that the star had been obliterated because it had gone too close to a Super Massive Black Hole we knew what we had observed was something even more extraordinary."

Super Massive Black Holes (SMBH) have been theoretically predicted by Einstein in 1915 but little is still known about them. "We know that they exist in the middle of galaxies and have three known traits, mass, spin and charge. The first two of these can be measured but the third cannot. We do know if something goes into a SMBH it will never be seen again," says Dr Sean Farrell. "So to have witnessed such a rare event provides us with an incredible opportunity to study what happens to stars when they get too close to the edge of a SMBH."

Farrell says that these observations will be important for testing theories on gravity as well as helping us understand how SMBH grow or 'feed'. "Black holes are crucial in how galaxies form and evolve. This is very important as their influence on galaxies has an enormous effect on gas, stars, planets and, of course, life itself," Farrell explains. "By studying the boundaries of black holes we can gain crucial knowledge about these extreme objects and their impact in the universe."

The team's paper: "Discovery of an ultrasoft X-ray transient source in the 2XMM catalog: a tidal disruption event candidate". Authors: Dacheng Lin (IRAP, France), Eleazar Carrasco (Gemini, Chile), Dirk Grupe (Penn State, USA), Natalie Webb (IRAP, France), Dider Barret (IRAP, France), and Sean Farrell (USyd, Australia) will be published in the Astrophysical Journal.

Contact: Dr Sean Farrell

Phone: 02 9351 7688

Email: 0211031a1a0934300a540e070e0b400d0d2f37572d29074b262f