The Herschel space observatory has made detailed observations of surprisingly hot gas that may be orbiting or falling towards the supermassive black hole lurking at the center of our Milky Way galaxy. Herschel is a European Space Agency mission with important NASA participation.
"The black hole appears to be devouring the gas," said Paul Goldsmith, the U.S. project scientist for Herschel at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This will teach us about how supermassive black holes grow."
Our galaxy's black hole is located in a region known as Sagittarius A* -- or Sgr A* for short -- which is a nearby source of radio waves. The black hole has a mass about four million times that of our sun and lies roughly 26,000 light-years away from our solar system.
Even at that distance, it is a few hundred times closer to us than any other galaxy with an active black hole at its center, making it the ideal natural laboratory to study the environment around these enigmatic objects. At Herschel's far-infrared wavelengths, scientists can peer through the dust in our galaxy and study the turbulent innermost region of the galaxy in great detail.
The biggest surprise was the hot gas in the innermost central region of the galaxy. At least some of it is 1,832 degrees Fahrenheit (around 1,000 degrees Celsius), much hotter than typical interstellar clouds, which are usually only a few tens of degrees above absolute zero, or minus 460 degrees Fahrenheit (minus 273 degrees Celsius).
The team hypothesizes that emissions from strong shocks in highly magnetized gas in the region may be a significant contributor to the high temperatures. Such shocks can be generated in collisions between gas clouds, or in material flowing at high speeds.
Using near-infrared observations, other astronomers have spotted a separate, compact cloud of gas amounting to just a few Earth masses spiralling toward the black hole. Located much closer to the black hole than the reservoir of material studied by Herschel in this work, it may finally be gobbled up later this year.
Spacecraft, including NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the Chandra X-ray Observatory, will be waiting to spot any X-ray burps as the black hole enjoys its feast.
Herschel is a European Space Agency mission, with science instruments provided by consortia of European institutes and with important participation by NASA. NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory, Pasadena, Calif. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena, supports the United States astronomical community. Caltech manages JPL for NASA.
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