Discovering a galaxy without dark matter, however, is a mystery

The mystery of the galaxy NGC 1277 is currently unexplained: this object, much larger than the Milky Way, in fact seems to be completely devoid of dark matter, the mysterious component that makes up about 25% of the universe and which, for such a large galaxy, should instead make up 10% to 70% of its mass. The discovery, published in the journal Astronomy and Astrophysics by a group led by the Canary Islands Institute of Astrophysics, challenges current theories that explain the universe, the so-called Standard Cosmological Model.

Dark matter is a type of matter that does not interact in the same way as normal matter: the only evidence of its existence is the strong gravitational pull it exerts on stars and gases, an attraction that is clearly seen in large galaxies. Researchers led by Sebastien Comeron analyzed NGC 1277, the story of a giant galaxy that formed in the early universe, to understand how dark matter affected its mass distribution, but instead found that this component had no place in the data collected.

The study’s authors propose two possible explanations: the first hypothesis is that gravitational interaction within the cluster of which the galaxy is a part, over time has shredded the dark matter, and the second instead suggests that dark matter may have already been expelled at the time of the formation of NGC 1277, which was born from the merger of protogalaxy fragments. However, for the researchers, neither of these two explanations is satisfactory, so the mystery remains unsolved for the time being.