Scientists have always looked for alien signals in space and sometimes when they get it, it keeps them baffled for years.

Esra Bulbul of the Harvard Center for Astrophysics said that what she and her team found in July 2014 "could not be explained by known physics.” She was referring to the strange signal that came from the Perseus Cluster - one of the biggest known objects in space today. The signal did not appear to originate from any type of known matter, The Daily Galaxy revealed.

She has been observing the Perseus Cluster, around 250 million light years from Earth, using the Chandra X-Ray Observatory. It was in 2012 when Bulbul saw the line pop up. She said that it took some time for her to acknowledge that the strange signal or line was not a known atomic line or a detector artefact.

The strange lines that scientists can map through Chandra came from ions in the atmosphere of the cluster. Ions like Fe XXV, Si XIV, and S XV produces a "line" or "bump" in the x-ray spectrum.

According to Bulbul, she has checked the data carefully, analyzed it again and divided it into subgroups. None of the things she did, like checking data through four other detectors on different observatories, could erase the strange signal or the line that popped out.

Europe’s XMM-Newton, a completely independent x-ray telescope, also confirmed the line. The data from the x-ray telescope showed the spectral signature showing up in the X-ray emissions of 73 other galaxy clusters. Since the spectral line does not appear to be related to any known type of matter, another theory emerged -- it could be dark matter.

Bulbul added that some physicists have referred to it as the "bulbulon." Theoreticians, on the other hand, proposed 60 different dark matter types to explain the line after Bulbul and her team submitted the paper.

The story continues until now. According to the Daily Galaxy, astronomers would need to further observe the Perseus cluster and similar objects.

Nicholas Jennings, from Oxford University and a co-author of a new study, said that studying what was found from the Perseus cluster and those of other observatories may lead to understanding what the dark matter is, including what are the strange x-ray signals seen from Perseus.

Interestingly, another set of astronomers found a second galaxy without dark matter in it. The team found NGC 1052-DF4 (DF4 for short), which is the second galaxy aside from NGC 1052-DF2 (yep, DF2 for short), to be completely lacking dark matter. Astronomer Shany Danieli of Yale University said that they wish to understand more about these galaxies to also progress in understanding dark matter - one of the biggest mysteries in the universe.

Black Hole
Scientists continue to study the nature of dark matter. Pictured: In this handout from NASA/ESA, an artist's concept illustrates a quasar, or feeding black hole. NASA's Wide-field Infrared Survey Explorer (WISE) revealed millions of potential black holes in its survey of the sky in 2011. NASA/Getty Images