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A* by the Chandra X-ray Observatory 
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Joined: Fri Mar 13, 2009 4:18 pm
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The Chandra X-ray Observatory recently posted some of the best images of Sagittarius A* and the area immediately surrounding it that have every been produced. Chandra's X-ray detector sees right through the gas and dust between Earth and the galactic center, capturing fairly clear views of the X-rays given off by the energetic dust swirling around A*.

Composite view of the Galactic Center
The Hubble, Spitzer, and Chandra observatories combined views in their respective bandwidths to create a very nice multi-band view of the galactic core, released back in November:

image by NASA (source)

This is false color: Hubble's near-infrared component is yellow, Spitzer's infrared is red, and Chandra's X-ray component is blue and violet. A* is the bright white/yellow snarl at mid-right. The blue blob to the left is thought to be a black hole or neutron-star binary--probably much closer to us than the galactic center, but the article didn't say.

Chandra's X-ray view by itself:

image by NASA (source)

I had to crop the sides of these two slightly to fit them on the forum, so click the "source" links if you want to see the original uncropped versions.

Chandra's long exposure of A*
At the beginning of this month, Chandra released an image made by staring at A* for nearly two weeks, which is a remarkably long exposure. This yielded what is probably the sharpest image of A* to date, in false color X-rays:

image by NASA (source)

Here you can clearly see the clouds of hot gas that extend for a dozen light years or so around the supermassive black hole: the light-blue blob to the upper left of A* (which is the bright white spot at center) is Sagittarius A East, the remnant of a supernova explosion, and the orangey-red clouds are the superheated gasses called Sagittarius A West.

The article accompanying the image (top link) provides a newly detailed description of the gas dynamics around A*: they think the heat of the extremely hot gas at the supermassive black hole's event horizon conducts to the gas further out--around the hot young stars near A* that are the source of much of the gas it "eats"--energizing that gas, which makes it heat up and create pressure that pushes away most of the other gas in the galactic center.

This mechanism by which supermassive black holes at the center of galaxies end up repelling the gas around them for several hundreds of millions of years, until the gas clumps up and reaches a mass critical enough to overcome the hole's "wind" and fall into the center, superheating and producing what's called a "quasar" or "active galactic nucleus," was already known in general, but the sharper data they're getting from these new observations is helping scientists start to break it down and describe the component mechanisms in more detail.

Tue Jan 19, 2010 7:41 pm
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