Astronomers believe that dark matter makes up about 85 percent of matter in the universe but while it had been over 70 years since it was first theorized, scientists had difficulty finding a tangible evidence of its existence.

A team of researchers, however, may have finally seen the first sign of the elusive dark matter, which is so-called because it does not absorb and emit light and thus cannot be directly observed. Scientists know that it exists though because of its gravitational interaction with the normal matter that can be seen and touched.

Alexey Boyarsky, from Leiden University in the Netherlands, and colleagues noticed a bizarre spike in X-ray emissions from the Andromeda galaxy and the Perseus galaxy cluster, while looking at the data collected by the XMM-Newton spacecraft, an  X-ray observatory of the European Space Agency (ESA).

All atoms are known to emit a distinct pattern of light known as spectrum and this is how scientists are able to know what celestial objects such as stars and planets are made of even from great distances. While studying the spectrum from the Andromeda galaxy and the Perseus galaxy cluster, however, the researchers have detected spikes where nothing should exist.

Because the signal does not correspond to any known particle or atom, the researchers suspect it may have been produced by dark matter.  The research team thinks it is the result of the particles of dark matter that decay and shoot out particles of light, or photons.  

Interestingly the signals' distribution corresponds to where a bulk of the concentration of dark matter theoretically exists.

"The relative fluxes for the two objects are in agreement with what is known about their DM distributions," the researchers wrote. "We also study surface brightness profiles of this line and find them consistent with expectations for a DM decay line."

The researchers also looked at the data from the Milky Way and found that the same signal they could not attribute to normal matter are in areas where dark matter should be present to keep the galaxy spinning.

 "After we saw the signal from the Perseus Cluster and the Andromeda galaxy we knew there should be a signal from the centre of our own galaxy, The Milky Way, as there is a lot of Dark Matter there," said study researcher Oleg Ruchayskiy, from EPFL's Laboratory of Particle Physics and Cosmology (LPPC) in Switzerland. "We did this analysis and we found the signal with the intensity of what we would expect."