May 7, 2013
Sagittarius A Black Hole To Devour Hot Molecular Gas
Lee Rannals for redOrbit.com - Your Universe Online
The European Space Agency's (ESA) Herschel spacecraft has revealed that the supermassive black hole in the center of our galaxy is about to get a taste of some hot molecular gas.
Sagittarius A has a mass of about four million times that of our Sun and sits about 26,000 light-years away from us. It is a few hundred times closer to us than any other galaxy with an active black hole at its center, making it ideal for studying these mysterious objects.
Astronomers have to use far-infrared wavelengths to see through all the dust that blocks the view of Sagittarius A, making the Herschel Space Observatory a great tool for scientists to observe our nearest black hole neighbor. This space observation center has detected a variety of simple molecules around Sagittarius A, including carbon monoxide, water vapor and hydrogen cyanide. Seeing these molecules allows astronomers to probe some of the fundamental questions about the properties of the interstellar gases surrounding the black hole.
“Herschel has resolved the far-infrared emission within just 1 light-year of the black hole, making it possible for the first time at these wavelengths to separate emission due to the central cavity from that of the surrounding dense molecular disc,” says Javier Goicoechea of Spain´s Centro de AstrobiologÃa, lead author of the paper that appeared in the Astrophysical Journal Letters.
ESA said the biggest surprise to the scientists observing Sagittarius A was how hot the molecular gas in the innermost central region of the Milky Way gets. This gas can reach temperatures around 1,832 degrees Fahrenheit. Goicoechea and his team believe that emissions from strong shocks in highly-magnetized gas in the region may be a significant contributor to the high temperatures.
“The observations are also consistent with streamers of hot gas speeding towards Sgr A*, falling towards the very centre of the Galaxy,” says Dr Goicoechea. “Our Galaxy´s black hole may be cooking its dinner right in front of Herschel´s eyes.”
Before material falls into a black hole, it is heated up, causing high-energy X-ray and gamma-ray flares. Currently, Sagittarius A is not showing any sign of this activity, but this is expected to change soon. Another compact cloud of gas the size of a few Earth masses is also spiraling towards the black hole, and it could be getting gobbled up later this year.
“The centre of the Milky Way is a complex region, but with these Herschel observations, we have taken an important step forward in our understanding of the vicinity of a supermassive black hole, which will ultimately help improve our picture of galaxy evolution,” says GÃ¶ran Pilbratt, ESA´s Herschel project scientist.