Herschel Finds Our Galaxy’s Black Hole Likes Hot Meals!
In a region near the center of our Milky Way galaxy known as Sagittarius A* (Sgr A*, and yes, the * IS pronounced! - ‘Sagittarius A-Star‘) lurks a Supermassive Black Hole. Apparently this local black hole of ours is preparing for a meal of hot gas.
With a mass of about 4 million times that of our Sun, and lying around 26,000 light-years away from our Solar System, our black hole is still a few hundred times closer to us than any other galaxy with an active black hole at its center. Detailed observations made by the European Space Agency’s (ESA) Herschel Space Observatory, (you know, BEFORE it did that whole running out of liquid helium coolant thing, So Long, Herschel), show hot molecular gas which may be orbiting or falling towards our hungry black hole.
Vast amounts of dust lie in the plane of the Milky Way between here and its center. At far-infrared wavelengths it’s possible to peer through the dust allowing Herschel’s scientists the chance to study the innermost region of our Galaxy in great detail. According to ESA (Herschel Reveals The Milky Way’s Warm Heart) new research based on spectroscopic data from Herschel has resolved the innermost portion of the Milky Way, a few light-years around Sgr A*, for the first time at far-infrared wavelengths. The team of astronomers, led by Javier Goicoechea from the Centro de Astrobiología in Madrid, Spain, was able to isolate the far-infrared emission from all the interstellar components that surround Sgr A* – neutral atomic, molecular and ionized gas, as well as dust.
A big surprise found by the team was how hot the molecular gas in the innermost central region of the Galaxy gets. At least some of it is around 1000ºC, much, MUCH, hotter than typical interstellar clouds (usually only a few tens of degrees above the –273ºC of absolute zero). Some of the heating is explained by the intense ultraviolet radiation coming from a cluster of massive stars which hang out very close to the Galactic Center, but they alone aren’t enough to explain the high temperatures. In addition to this stellar radiation, Dr Goicoechea’s team hypothesize that emission from strong shocks in highly-magnetized gas in the region may be contributing to the high temperatures. Shocks such as these may be generated in gas cloud collisions, or in material flowing at high speed from stars and protostars.
‘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.’
To get a head-wrapping perspective on where this hot action is taking place in relation to our little neighborhood in the Orion Arm of the galaxy, check out this map of the Milky Way provided by Richard Powell. Also check out his web-site, The Atlas of The Universe, for an incredibly awesome and completely addictive interactive version of this map, as well as other equally time-devouring maps!