Galactic Antimatter

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The Moon passes through the heart of the Milky Way early tomorrow. It's above the spout of the teapot-shaped constellation Sagittarius, which is low in the south at first light. The heart of the galaxy lies in that direction -- about 27,000 light-years away. We can't see it because thick clouds of dust block the light from the galaxy's center.

If our eyes were sensitive to other wavelengths of light, though, we'd see a lot. In the infrared, for example, we'd see the glow of the dust clouds. And in gamma rays, we'd see the glow of particles of matter and antimatter annihilating each other.

A cloud of antimatter extends hundreds of light-years from the center of the galaxy. But finding its source has been a problem. Some scientists had suggested it was produced when particles of "dark matter" slammed into each other, or into particles of normal matter.

Observations by a European gamma-ray satellite have led to a different conclusion. They show that the cloud of antimatter is much larger to the west of the galactic center than to the east.

From this off-center arrangement, a team of researchers has suggested that the antimatter comes from disks of superhot gas around black holes or neutron stars. These disks can get so hot that they create particles of matter and antimatter. Powerful magnetic fields shoot them far out into space, where they ram together and cancel each other out -- creating a soft glow of gamma rays.

Script by Damond Benningfield, Copyright 2008

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