The signal appeared in the X-ray spectrum as a weak, atypical photon emission that could not be attributed to any known form of matter, the researchers said.
Above all, "the signal's distribution within the galaxy corresponds exactly to what we were expecting with dark matter, that is, concentrated and intense in the center of objects and weaker and diffused on the edges," said Oleg Ruchayskiy, scientist at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland.
"With the goal of verifying our findings, we then looked at data from our own galaxy, the Milky Way, and made the same observations," Alexey Boyarsky, professor at the Leiden University in the Netherlands, added.
Dark matter, which appears to make up at least 80 percent of the universe, up to now has been purely hypothetical.
It is run by none of the standard models of physics other than through the gravitational force.
So if the discovery is confirmed, "it could usher in a new era in astronomy," Ruchayskiy said.
For the study, the researchers collected thousands of signals from the European Space Agency's XMM-Newton telescope and eliminated all those coming from known particles and atoms.
They then detected an anomaly that, even considering the possibility of instrument or measurement error, caught their attention.
The study is forthcoming in the journal Physical Review Letters.
