Does our galaxy center around a mass of dark matter? A new analysis that examines the steady stream of gamma rays that the Fermi Space Telescope has been picking up since its launch six years ago suggests that it might.
So, how did scientists come to this conclusion?
They started with a map, charting out the points where the radiation had been picked up and its intensity. Then, they simply subtracted the radiation that they could account for using known sources — everything from pulsars to supernova remnants to clouds of interstellar gas.
But, after all that, they were still left with a mysterious patch of remaining radiation, spanning a distance of over 5,000 light years from the galaxies center and measuring at between 1 and 3 billion electron volts.
This mysterious patch can be made a lot less mysterious, though, with the addition of one factor: dark matter. Which, as currently theorized, could account for both the presence and scope of the otherwise unexplained patch of radiation, as lead author of the study Dan Hooper of the Fermilab explains:
The new maps allow us to analyze the excess and test whether more conventional explanations, such as the presence of undiscovered pulsars or cosmic-ray collisions on gas clouds, can account for it. The signal we find cannot be explained by currently proposed alternatives and is in close agreement with the predictions of very simple dark matter models.
So, with all this, does this mean we finally have the smoking gun that proves dark matter is at the center of the Milky Way?
Well, not quite. The findings — which are detailed in both a paper published in Physical Review D and a more recent working paper up on ArXiv — are, as yet, unconfirmed. Its possible that there is another unknown source for the measured radiation.
Still, the data does make for what NASA calls the "strongest case to date" that the dark matter scientists have long suspected lies at the center of our galaxy is really out there.
Images: NASA Goddard