NASA's Fermi detects evidence of dark matter in Andromeda galaxy

Image credits: NASA/DOE/Fermi LAT Collaboration and Bill Schoening, Vanessa Harvey/REU program/NOAO/AURA/NSF

New Delhi: NASA says a mysterious signal found at the center of the neighboring Andromeda galaxy could indicate the presence of dark matter.

Interestingly, the gamma-ray signal detected by the Fermi Gamma-ray Space Telescope is similar to one seen by Fermi at the center of our own Milky Way galaxy.

What's surprising is that the latest data from Fermi shows the gamma rays in Andromeda - also known as M31 - are confined to the galaxy’s center instead of spread throughout.

According to scientists, this unusual distribution suggests that the emission may come from several undetermined sources and one of them could be dark matter - an unknown substance that makes up most of the universe.

Another possible source for this emission could be a rich concentration of pulsars in M31’s center, NASA said.

Video credit: NASA Goddard/YouTube

Gamma rays are the highest-energy form of light, produced by the universe’s most energetic phenomena. They’re common in galaxies like the Milky Way because cosmic rays, particles moving near the speed of light, produce gamma rays when they interact with interstellar gas clouds and starlight.

“We expect dark matter to accumulate in the innermost regions of the Milky Way and other galaxies, which is why finding such a compact signal is very exciting,” said lead scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research and the Research Institute in Astrophysics and Planetology in Toulouse, France. “M31 will be a key to understanding what this means for both Andromeda and the Milky Way.”

With Fermi detecting a similar gamma-ray signature in both M31 and the Milky Way, scientists believe that they can use this information to solve mysteries within both galaxies

We don’t fully understand the roles cosmic rays play in galaxies, or how they travel through them,” said Xian Hou, an astrophysicist at Yunnan Observatories, Chinese Academy of Sciences in Kunming, China, also a lead scientist in this work. “M31 lets us see how cosmic rays behave under conditions different from those in our own galaxy.”

While more observations are necessary to determine the source of the gamma-ray excess, the discovery provides an exciting starting point to learn more about both galaxies, and perhaps about the still elusive nature of dark matter.

“We still have a lot to learn about the gamma-ray sky,” said co-author Regina Caputo, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Caputo said. “The more information we have, the more information we can put into models of our own galaxy.”

A paper describing the new findings will appear in an upcoming issue of The Astrophysical Journal.