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When you drive toward the downtown of any city on a clear, dark night, you can see a dome of light above it from miles away. Astronomers can see a similar glow from the downtown region of the Milky Way galaxy — a glow of gamma rays.
That region of the galaxy is in the constellation Sagittarius, which scoots low across the south on summer nights. Its brightest stars form the outline of a teapot.
The galaxy’s downtown is just above the spout of the teapot, although it’s hidden from human eyes behind clouds of dust. But gamma rays go right through the dust. In fact, they’re the most powerful form of energy.
The gamma-ray glow around the center of the Milky Way may be produced by dark matter — a form of matter that emits no detectable energy, but that exerts a gravitational pull on the matter around it. There appears to be about fives times more dark matter than the “normal” matter that makes up stars, planets, and people.
Dark matter may consist of heavy subatomic particles, known as WIMPs. They may occasionally ram together, producing gamma rays. And several teams of scientists say the gamma-ray glow from the Milky Way is a good match for what they’d expect collisions between WIMPs to look like.
Others, though, say the glow comes from thousands of rapidly spinning corpses of once-mighty stars.
Astronomers continue to watch the glow from the center of the Milky Way to better understand conditions in the galaxy’s busy downtown.
Script by Damond Benningfield