ESO’s Very Large Telescope has made detailed observations of a hot gas cloud being ripped apart by the supermassive black hole at the center of our Galaxy.
New observations from ESO’s Very Large Telescope show how a gas cloud now passing close to the supermassive black hole at the centre of the galaxy is being ripped apart. The horizontal axis shows the extent of the cloud along its orbit and the vertical axis shows the velocities of different parts of the cloud. The cloud is now dramatically stretched out and the velocity of the front is several million km/h different from that of the tail (ESO / S. Gillessen)
In 2011, VLT discovered a gas cloud with several times the mass of the Earth accelerating towards the black hole. This cloud is now making its closest approach and new observations show that it is being stretched by the black hole’s extreme gravitational field.
Dr Stefan Gillessen from Max Planck Institute for Extraterrestrial Physics, Germany, who is a lead author of a paper reporting the results in the Astrophysical Journal (preprint at arXiv.org / full paper from ESO), said that the gas at the head of the cloud is now stretched over more than 160 billion km around the closest point of the orbit to the black hole. And the closest approach is only a bit more than 25 billion km from the black hole itself – barely escaping falling right in.
“The cloud is so stretched that the close approach is not a single event but rather a process that extends over a period of at least one year.”
As the gas cloud is stretched its light gets harder to see. But by staring at the region close to the black hole for more than 20 hours of total exposure time, the astronomers were able to measure the velocities of different parts of the cloud as it streaks past the black hole.
“The most exciting thing we now see in the new observations is the head of the cloud coming back towards us at more than 10 million km/h along the orbit — about 1% of the speed of light. This means that the front end of the cloud has already made its closest approach to the black hole,” said co-author Dr Reinhard Genzel of the University of California, Berkeley.
This simulation of a gas cloud passing close to the supermassive black hole at the centre of the galaxy shows the situation in mid-2013 (ESO / S. Gillessen / MPE / Marc Schartmann)
The origin of the gas cloud remains mysterious, although there is no shortage of ideas. The new observations narrow down the possibilities.
“Like an unfortunate astronaut in a science fiction film, we see that the cloud is now being stretched so much that it resembles spaghetti. This means that it probably doesn’t have a star in it. At the moment we think that the gas probably came from the stars we see orbiting the black hole,” Dr Gillessen concluded.
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Bibliographic information: Stefan Gillessen et al. 2013. Pericenter passage of the gas cloud G2 in the Galactic Center. ApJ, in press; arXiv: 1306.1374
