Hints that dark matter could be crashing and burning in the centre of the Milky Way might themselves be going up in smoke. A search for nearby dwarf galaxies that should show the same signal have proved fruitless, leaving physicists disappointed after five years of excitement.
The signal first emerged in 2010, when Dan Hooper of the Fermi National Accelerator Laboratory and colleagues found an unexpectedly bright gamma ray glow in data from the Fermi Gamma-Ray Space Telescope. They interpreted it as the debris left behind when particles of dark matter – the mysterious substance that makes up most of the matter in the universe yet refuses to interact with ordinary matter except through gravity – crashed together and annihilated each other in the centre of the Milky Way.
At the time, nobody could explain the glow in less exotic terms. And what’s more, the theory fitted well with what physicists expected might happen if dark matter was made up of relatively lightweight particles, with a mass of about 10 to 50 gigaelectronvolts (GeV).
In 2013, Hooper and Tracy Slatyer at the Massachusetts Institute of Technology boosted the case further by showing similar signals just outside the galaxy’s core.
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