If our best sign yet of dark matter is what it seems, then the supermassive black hole at the centre of our galaxy is a complex beast.
Dark matter is thought to make up 80 per cent of the universe's matter, but it is hard to detect as it scarcely interacts with other matter. One way to sense it indirectly is through high-energy photons emitted when two dark matter particles collide and annihilate each other.
NASA's Fermi space telescope has seen signs of such photons around the supermassive black hole at the centre of the Milky Way, where dark matter is expected to cluster. Some think it is our best sign of dark matter so far.
But now Jessie Shelton at the University of Illinois at Urbana-Champaign and her colleagues argue that if the signal is truly from dark matter, it is an order of magnitude too weak to match up with conventional ideas of how the black hole formed.
"If the simplest model of black hole formation is the true history of our galaxy, then no reasonable dark matter candidate can be responsible for generating the Fermi excess," she says.To read more, click here.