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A controversial dark matter claim may be making a comeback. Three years ago, a team of particle astrophysicists appeared to nix the idea that a faint glow of gamma rays in the heart of our Milky Way Galaxy could be emanating from dark matter—the mysterious stuff whose gravity holds the galaxy together. But the conclusion that the gamma rays come instead from more ordinary sources, such as spinning neutron stars known as pulsars, may have been too hasty, the team reports in a new study. So the dark matter hypothesis may alive and well after all.
“I’m sure that some people will start to think about dark matter interpretations [of the glow] again,” says Dan Hooper, a theorist at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, who was not involved in either study. Others are less sure there will be such a revival.
Hooper - Fermilab - Colleague - Lisa - Goodenough
Hooper and his Fermilab colleague Lisa Goodenough discovered the unexplained gamma ray glow in 2009 while studying data from NASA’s orbiting Fermi Gamma-ray Space Telescope. Dubbed the galactic center excess, that glow enshrouds the heart of the galaxy. Draw a circle on the sky around the galactic center 30° in radius and the excess will account for 2% of all gamma rays coming from within it.
Hooper and Goodenough immediately suggested the glow could be evidence of dark matter. Physicists think the entire Milky Way Galaxy lies embedded in a vast cloud of dark matter, like the swirl of color within a marble, with the dark matter densest in the middle. And theory generally suggests that, rarely, when two dark matter particles collide they should annihilate each other to produce ordinary particles, such as the observed high energy photons, or gamma rays. The discovery of the galactic center excess touched off a frenzy of “model building,” in which...
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