Geringer-Sameth & Walker/Carnegie Mellon University
By Dennis Overbye
A small, newly discovered galaxy orbiting the Milky Way is emitting a surprising amount of electromagnetic radiation in the form of gamma rays, astronomers reported Tuesday. The finding may be the latest in a long string of cosmic false alarms, they said, or it might be that the mysterious dark matter that permeates the universe is finally showing its face.
If confirmed, the results could mean that most of the matter of the universe is in the form of as-yet-unidentified elementary particles, 20 to 100 times as heavy as a proton, that have been drifting and clumping like fog in space ever since the Big Bang.
But while the gamma-ray signal is “tantalizing,” in the words of Alex Geringer-Sameth of Carnegie Mellon University and colleagues from Brown and Cambridge Universities, “it would be premature to conclude it has a dark matterorigin.” Their analysis appears in a papersubmitted to the journal Physical Review Letters.
The group used data from NASA’s Fermi Large Area Telescope, which orbits the Earth, to search for gamma rays from a loose-looking accumulation of stars known as Reticulum-2, in the southern constellation of the same name. It is one of a rare breed known as dwarf galaxies, which can have fewer than a hundred stars and are only a billionth as luminous and a millionth as massive as the Milky Way.
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