Scientists in Boston have released an image
which they say could be the first time dark matter has ever been
captured on a Nasa telescope. The new study of gamma rays captured by
the US space agency's Fermi apparatus picked up a signal which "cannot
be explained by other alternatives" - meaning that by process of
elimination what we are seeing has a high chance of being the elusive
substance. Dark matter makes up most of the material universe - yet we
know very little about what it consists of or how it interacts with
everything else.
But by analyzing an image of gamma rays coming from the Milky Way, a
joint team from Harvard, the University of Chicago and MIT in Boston
have been able to pick out a bright core at the centre of our galaxy
that is only currently explained by models of dark matter itself.
Experts have speculated for some time that dark matter is most likely to
be observed at the centre of the galaxy - large quantities of dark
matter attract normal matter, forming a foundation upon which visible
structures, such as galaxies, are built.
"This is the most compelling signal we've had for dark matter particles -
ever," said Dan Hooper, speaking to New Scientist from the Fermi
National Laboratory in Batavia, Illinois. "At this point, there are no
known or proposed astrophysical mechanisms or sources that can account
for this emission," he said. "That doesn't rule out things that no one's
thought of yet, but we've tried pretty hard to think of something
without success. " The team took publicly available images of gamma ray
light shot out from the Milky Way and, piece by piece, removed every
pixel that could be explained by a known phenomenon like a supernova or
particles colliding with interstellar gas.
The team took publicly available images of gamma ray light shot out from
the Milky Way and, piece by piece, removed every pixel that could be
explained by a known phenomenon like a supernova or particles colliding
with interstellar gas. "Our case is very much a process-of-elimination
argument. We made a list, scratched off things that didn't work, and
ended up with dark matter," said co-author Douglas Finkbeiner, a
professor of astronomy and physics at Harvard. One possible theory
suggests that dark matter is made up of brilliantly named Weakly
Interacting Massive Particles - or Wimps - which would collide to
produce gamma rays at the energies detected by the Fermi telescope.
Tracy Slatyer, a theoretical physicist at MIT, said: "This is a very
exciting signal, and while the case is not yet closed, in the future we
might well look back and say this was where we saw dark matter
annihilation for the first time."