NASA's Fermi telescope has detected gamma-ray signals at the center of Andromeda galaxy indicating the presence of dark matter in the nearest galaxy to Milky Way.
The signals point to the presence of invisible dark matter as their key source, whose presence in Milky Way has already been captured by Fermi.
Andromeda or M31 is 2.5 million light-years away from Earth.
Dark matter — the mysterious substance makes the bulk of the universe and its presence is experienced by the effects of gravitation.
Gamma-rays emanate from a high energy phenomenon that takes place in galaxies like the Milky Way.
"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 chief scientist Pierrick Martin, an astrophysicist at the National Center for Scientific Research in Toulouse, France.
Gamma-rays are generated from cosmic rays which are particles that move at a huge velocity equaling the speed of light and collide with gas clouds and starlight bursting energy that shows up as gamma-rays.
Weakly-interacting massive particles (WIMPS) are one form of dark matter particles that clash and produce gamma-rays. It is believed that the gamma-emitting region spotted by Fermi could be housing dark matter clouds.
The Fermi data show a concentration of gamma-rays in Andromeda's center instead of having a broad spread. Besides dark matter, other sources of gamma emissions are pulsars which are neutron stars.
Milky Way Similar To Andromeda
As mentioned, Fermi has already spotted gamma-rays in the Milky Way and presence of dark matter has been a foregone conclusion.
On dark matter in M31, more validation will be required from observations to identify the source of gamma-rays and the new data will do good in serving as a stepping stone for more studies.
The advantage will be that scientists can compare Milky Way and Andromeda data for greater accuracy. That limited volume of gamma-rays from the big disk of M 31 implies that there are fewer cosmic rays in the stars forming region.
Since cosmic rays are linked to star formation, the concentration of gamma rays in the center of M 31 with sparse distribution in the outer parts means the galaxy has a different way in cosmic ray production or is helping the faster escape of gamma-rays.
The discovery can also help in comprehending the life cycle of cosmic rays and their role in star formation.
Milky Way is similar to Andromeda and more can be learned about the galaxy, according to Regina Caputo, a scientist at Goddard Space Flight Center of NASA in Maryland.
There is still a lot to learn about the gamma-ray sky and the new information will help in adding to the models of Milky Way for further study.
Pulsar Connection
Another source is clustering pulsars that wield intense signals of gamma rays.
In the Milky Way, gamma-ray radiation is found at the core. By comparing signals from Andromeda and Milky Way, it can be verified if the signal was emitted by pulsars or dark matter particles in the cores of these galaxies.
The results of the study will appear in the Astrophysical Journal.
