Dark matter protects dwarf galaxies from destruction

The Big Dipper III/UNIONS 1

04. April 2024 5:07 p.m. Robert Klatt

The dwarf galaxy UMa3/U1 contains only 60 stars and is still not torn apart by the Milky Way because it is held together by dark matter.

Victoria (Canada). In astronomy, dark matter is used to explain the movements of galaxies in the universe. Although the existence of dark matter has not yet been proven experimentally, science accepts it because dark matter answers various fundamental questions in astrophysics. Researcher of University of Victoria (UVic) discovered an extremely faint dwarf galaxy that could not exist without dark matter.

According to the publication in The Astrophysics Journal The galaxy called Ursa Major III/UNIONS 1 (UMa3/U1) has only 60 stars and is more than ten billion years old. The small galaxy orbits the Milky Way, but has not yet been torn apart by it, suggesting it is held together by dark matter. Since small galaxies contain thousands or even millions of stars, the small number of stars in UMa3/U1 means that the galaxy likely has the largest proportion of dark matter among known objects in space.

Discovery with the Canada-France-Hawaii Telescopes (CFHT)

The galaxy neighboring the Milky Way was discovered using the Canada-France-Hawaii Telescope (CFHT), located on the Mauna Kea volcano in Hawaii. Observations of the galaxy show that it is also moving through the inner regions of the Milky Way. Furthermore, analyzes show that the stars of UMa3/U1 formed in the early days of the universe and are therefore extremely old.

According to astronomers, this clearly indicates that UMa3/U1 is a dwarf galaxy and not a star cluster, despite its unusually small number of stars. In addition, predictions from the Standard Model of Cosmology also suggest the existence of old, faint galaxies with a high proportion of dark matter. UMa3/U1 is therefore probably the darkest dwarf galaxy and closest to the Milky Way that science has observed to date.