Astronomers have discovered our little companion in our Milky Way Galaxy

The small galaxy, called UMa3/U1, is located in the well-known Ursa Major constellation, and is about 30,000 light-years away from us. Observations show that UMa3/U1 consists of about sixty stars that are more than 10 billion years old and are only about 10 light-years in size. In total, its mass is only sixteen times that of the Sun.

UMa3/U1 was first observed in data from the Northern Optical Ultraviolet and Near-Infrared Survey, conducted with the Canada-France-Hawaii Telescope and Pan-STARRS. Astronomers then examined the galaxy in more detail using the Deep Imaging Multi-Object Spectrograph (DEIMOS) at Keck Observatory. In this way they were able to confirm that UMa3/U1 are held together by gravity. This means it is a dwarf galaxy or star cluster.

Dropp off

It's not clear how these stars manage to remain such a close group. The object is so small that you would expect that the powerful tidal forces of our Milky Way Galaxy had already torn apart the star system and left no discernible remains. The fact that the galaxy appears intact leads to two equally interesting possibilities: either UMa3/U1 is a small galaxy settled with large amounts of dark matter, or it is a star cluster that was discovered by chance shortly before its demise.

In the first case, the existence of UMa3/U1 would support the prediction of the most popular theory about the origin of the universe. According to the Lambda Cold Dark Matter Model (LCDM), galaxies like the Milky Way must have accumulated satellite galaxies during their formation, which continue to orbit them to this day.