December 15, 2011
Gas Cloud En Route To Milky Way’s Black Hole
The massive black hole at the center of our Milky Way Galaxy is destined to be invaded by a gas cloud, creating a violent encounter, according to astronomers.The supermassive black hole in the Milky Way is close enough for astronomers to study in detail, so the encounter could provide a unique chance for scientist to observe what until now has only been theorized.
The astronomers plan to find out how a black hole eats up gas, dust and stars as it grows even bigger.
"When we look at the black holes in the centers of other galaxies, we see them get bright and then fade, but we never know what is actually happening," Eliot Quataert, a theoretical astrophysicist and University of California, Berkeley professor of astronomy, said in a press release.
"This is an unprecedented opportunity to obtain unique observations and insight into the processes that go on as gas falls into a black hole, heats up and emits light. It's a neat window onto a black hole that's actually capturing gas as it spirals in."
Reinhard Genzel, professor of physics at both UC Berkeley and the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, said that he is interested in finding out what the front row spectacle of the supermassive black hole will bring.
"The next two years will be very interesting and should provide us with extremely valuable information on the behavior of matter around such massive objects, and its ultimate fate," Genzel said in a press release.
Genzel and colleagues have seen the gas cloud about three times the mass of Earth speeding up and falling deeper into the gravitational whirlpool of the black hole since 2008.
They said that the edges of the gas cloud are beginning to fray.
"It is not going to survive the experience," first author Stefan Gillessen of the MPE said in a press release.
Gillessen built the infrared detector on the European Southern Observatory's Very Large Telescope in Chile, which is used to observe the movement of stars and gas in the center of the Milky Way Galaxy.
Scientists say that by 2013, outbursts of X-rays and radio waves will be emitted as the cloud gets hotter and is obliterated by the black hole. The cloud is mostly made up of hydrogen and helium gas.
The Chandra X-ray satellite has already scheduled its largest single chunk of observation time in 2012 near the Milky Way's central black hole.
Since MPE astronomers began observing the black hole in 1992, they have only seen two stars as close as this gas cloud to the black hole.
The difference between those stars and the gas cloud is that those stars "passed unharmed through their closest approach, (while) the gas cloud will be completely ripped apart by the tidal forces around the black hole," Gillessen said.
The cloud may have formed when gas pushed by stellar winds from two nearby stars collided. The cloud is glowing under the strong ultraviolet radiation from surrounding hot stars.
As the cloud falls towards the black hole at a velocity of 1,460 miles per second, it will interact with the hot gas present in the accretion flow around the black hole and become disrupted by turbulent interaction.
The scientists were able to simulate the time evolution of the cloud, and predict that the temperature of the gas cloud should increase rapidly to several million Kelvin, or 12,599,540 degrees Fahrenheit, near the black hole. The cloud is currently at 550 Kelvin, or 530 degrees Fahrenheit.
The research will be published in the journal Nature.
Image 1: This view shows a simulation of how a gas cloud that has been observed approaching the supermassive black hole at the center of the galaxy may break apart over the next few years. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013. The remains of the gas cloud are shown in red and yellow, with the cloud's orbit marked in red. The stars orbiting the black hole are also shown along with blue lines marking their orbits. This view simulates the expected positions of the stars and gas cloud in the year 2021. Credit: ESO/MPE/Marc Schartmann
Image 2: This simulated view shows a gas cloud (just above center, with its orbit shown in red) that has been observed approaching the supermassive black hole at the center of the Milky Way. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013. The stars orbiting the black hole are also shown along with blue lines marking their orbits. The stars and the cloud are shown in their actual positions in 2011. Credit: ESO
Image 3: These images taken over the last decade using the NACO instrument on ESO´s Very Large Telescope show the motion of a cloud of gas that is falling towards the supermassive black hole at the center of the Milky Way. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013. Credit: ESO/MPE
On the Net:
- University of California, Berkeley
- Max Planck Institute for Extraterrestrial Physics
- Very Large Telescope
- Chandra X-ray satellite
- Nature Paper