Science

Supermassive black hole at Milky Way's core gives up a secret (images)

For years, scientists puzzled over mysterious X-ray flares given off by Sagittarius A*. Now they've uncovered an explanation.

Charles Cooper

Charles Cooper was an executive editor at CNET News. He has covered technology and business for more than 25 years, working at CBSNews.com, the Associated Press, Computer & Software News, Computer Shopper, PC Week, and ZDNet.

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Charles Cooper

Feb. 14, 2012 8:17 a.m. PT

1 of 10 NASA/Chandra X-ray Observatory

Sagittarius A*

Sagittarius A*--or Sgr A*, as it's more commonly described--is a supermassive black hole at the center of our Milky Way. It's big and bad, containing about 4 million times the mass of our sun. It's also given to odd behavior; scientists say they can identify mysterious flares being emitted for a few hours each day.

After years seeking an explanation, astronomers using new data from the Chandra X-ray Observatory now think that they have found one: Sgr A* may simply be vaporizing and actually "devouring" asteroids that cross its path. Think of it as a galactic burp.

And there's no shortage of raw material for Sgr A* to consume. According to NASA, the cloud around Sgr A* contains literally trillions of asteroids and comets. Any celestial object passing with 100 million miles of the black hole--that's roughly the distance between Earth and the sun--would get obliterated. (We'd love to see how James T. Kirk could pull himself out of that one. Just saying.)

2 of 10 NASA/CXC/M.Weiss

Asteroids prior to turning into a black hole's feeding time

To get an idea of what this might look like, NASA offered this illustration of asteroids heading toward a black hole. The tidal forces generated by Sgr A* vaporize the asteroids. Flares get produced, and the remains of the asteroids eventually get swallowed up by the black hole.

3 of 10 NASA/CXC/MIT/Frederick K. Baganoff et al

Milky Way's giant black hole woke up 300 years ago

Despite the periodic flares, Sgr A*, our galaxy's central black hole, is considered to be something of a slumbering giant. A team of Japanese astronomers recently published their discovery that Sgr A* fired off a powerful flare about 300 years ago. Because of the great distances involved--the galactic center is about 26,000 light-years from Earth--astronomers are now observing events that occurred 26,000 years ago. "The black hole was a million times brighter three centuries ago. It must have unleashed an incredibly powerful flare," said Katsuji Koyama of Kyoto University, a co-author of a study, which appears in the Publications of the Astronomical Society of Japan.

4 of 10 NASA/CXC/UCLA/MIT/M.Muno et al.

A light echo from Sagittarius A*

Here's an amazing view of the middle of the Milky Way, with Sagittarius A* in the middle.

5 of 10 NASA

Stages of star formation

The different stages of star formation around a black hole. (The upper panel shows that the cluster's early formation is shown with red gas.) A supermassive black hole surrounded by a disk of red-and-yellow gas is to the right. The lower panel shows the stars are heading in the direction of the supermassive black. Eventually, the star cluster will get ripped apart by the black hole's gravity pull.

6 of 10 NASA/CXC/M.Weiss

A star is born - around a black hole

Here is an artist's depiction of star formation around a black hole. In this illustration, the massive stars are colored in blue, while the small disks represent stars that are still forming.

7 of 10 NASA/CXC/UCLA/MIT/M.Muno et al.

130 light year region in the center of the Milky Way

NASA combined a dozen Chandra observations to reconstruct a color-coded 130 light-year region in the center of the Milky Way. Red represents low, green represents medium, and blue represents high-energy X-rays. Shock waves from supernova explosions are thought to heat up the gas clouds from 10 million degrees to 100 million degrees along this ridge of Sgr A*.

8 of 10 NASA

A closer look at Sagitarrius A*

Here's another look at the black hole, this time using infrared light and X-ray light, which allowed astronomers to peer past space dust to observe the activity near the galaxy's core. You can locate center of the galaxy within the bright-white region of the image.