LONDON, Jan. 18 (UPI) -- A NASA space telescope has seen hints of evidence for the so-called dark matter that makes up an estimated 85 percent of the universe's mass, researchers say.
In one of physics' greatest ongoing mysteries, evidence for the existence of dark matter comes only from its gravitational effects. It cannot be directly observed because it interacts only very weakly with light or normal matter.
The Fermi space telescope, designed to catch gamma rays -- the universe's highest-energy light -- has produced hints of its existence in gamma rays at the center of the Milky Way.
Fermi project scientist Julie McEnery said that has sparked a call for proposals to change the telescope's main mission from its current examination of the spinning neutron stars known as pulsars and supermassive black holes.
"Some of the motivation to explore different observation strategies is from this tentative signal at the center of the galaxy, but I think even if that wasn't there we would want to go to our community of scientists and ask them, 'based on what you've seen in the data, should we do something different?'" she told the BBC.
Physicists say they believe dark matter consists of relatively heavy particles which, when they encounter one another, "annihilate" with a flash of high-energy light that the Fermi telescope could see.
Seeing evidence for dark matter at the center of the galaxy would be the most important result the Fermi mission could produce, McEnery said.
"We'll have found something that physicists and astronomers have been looking for for decades -- understanding not just where dark matter is but something more fundamental about its nature, so this is something that we in the Fermi project are keen to pursue," she said.