Smallest star system near the Milky Way may be dominated by dark matter

The group of stars with the faintest brightness and lowest mass around the Milky Way ever observed was detected by a group of astronomers from the University of Victoria (Canada) and Yale University (United States). The system, which was named Ursa Major III/UNIONS 1 (UMa3/U1), may also be the one with the largest presence of dark matter already registered.

“UMa3/U1 is located in the constellation Ursa Major. It's in our cosmic backyard, so to speak, about 30 thousand light years from the Sun “, said in a statement Simon Smith, postgraduate student in astronomy at the University of Victoria and lead author of the study, published in the scientific journal The Astrophysical Journal.

“UMa3/U1 had escaped detection until now due to its extremely low light “, explained Smith.

According to the researchers, the small system is composed of about 60 stars with ages that may exceed 10 billion years of age and are spread over a distance of just 10 light years. The cluster is considered extremely light by astronomers, with a mass equivalent to just 16 times the mass of the Sun.

Telescope data confirmed that the system is linked by the gravitational interaction between stars, which means that UMa3/U1 can be considered a dwarf galaxy or a star cluster .

As it is a group of stars with an extremely low mass, scientists consider it a mystery that they are linked together by the gravity they exert on each other. One of the possible explanations would be the presence of dark matter to maintain the grouping.

“The object is so small that its long-term survival is very surprising. We might expect that the severe tidal forces of the Milky Way's disk have torn apart the system by now, leaving no observable remnants,” Will Cerny, a Yale University graduate student and second author of the study, said in the statement.

“The fact that the system appears intact leads to two equally interesting possibilities. Either UMa3/U1 is a small galaxy stabilized by large amounts of dark matter, or it is a cluster of stars that we observed at a very special moment before their imminent disappearance”, concludes the researcher.

Just like visible matter, dark matter occupies space in the Universe and has mass. Consequently, it can gravitationally interact with other bodies . However, This type of matter does not reflect, absorb or radiate light, making its detection very difficult . According to NASA (United States space agency), Scientists estimate that dark matter represents about 27% of the Universe , but it is still not possible to say exactly what it is or its origin. Today, researchers realize the existence of dark matter through the effects they observe in interactions between celestial bodies.

“If future observations confirm or reject that this system contains a large amount of dark matter, we are very excited about the possibility that this object could be the tip of the iceberg – that it could be the first example of a new class of extremely dark star systems. weaknesses that have escaped detection until now,” said Cerny.