1. A signal coming from the centre of the Milky Way could be the best sign of dark matter yet.
Dark matter is an elusive substance that makes up most of the matter in the universe, but which we’ve been unable to detect directly — yet. The centre of the galaxy is expected to harbour large amounts of the stuff.
The signal, made up of high-energy light called gamma rays, can’t be explained by known sources. But it does seem to fit with some forms of dark matter.
2. The gamma rays were detected by scientists looking at publicly available data from Nasa’s Fermi Gamma-ray Space Telescope.
This is a false colour image of the centre of the galaxy taken by the Fermi space telescope. All known gamma ray sources have been removed, so the red dot in the middle reveals the unexplained extra gamma rays that might be caused by dark matter.
3. What dark matter is actually made of is one of the biggest questions facing physics today.
WIMPs, or Weakly Interacting Massive Particles, are a leading candidate. There are several different types of (theoretical) WIMP, and many produce gamma rays that the Fermi experiment’s telescope would be able to detect.
What we do know is that dark matter makes up 27% of the total mass and energy of the universe. Normal matter makes up just 5% of the total universe.
4. There’s a one in 12 chance the signal is a fluke. Over the next few years the telescope will collect more data to confirm the finding. Fermi scientist Elliott Bloom says:
If we ultimately see a significant signal, it could be a very strong confirmation of the dark matter signal claimed in the galactic center.