A new study using NASA’s Chandra X-ray Observatory tracked two pairs of supermassive black holes in dwarf galaxies on their collision course. This is the first evidence of such an inevitable encounter, providing scientists with important information about the growth of black holes in the early universe.

By definition, dwarf galaxies contain stars with a total mass of less than 3 billion suns, or about 20 times that of the Milky Way. Astronomers have long suspected that dwarf galaxies, especially in the relatively early universe, merged to develop into the larger galaxies seen today. However, current technology cannot observe the first generation of merging dwarf galaxies because they are extremely dim at great distances. Another tactic – looking for closer mergers of dwarf galaxies – has so far been unsuccessful.

The new study addresses these challenges by conducting a systematic review of Chandra’s deep X-ray observations and comparing them with infrared data from NASA’s Wide Infrared Survey Explorer (WISE) and optical data from the Canada-France-Hawaii Telescope (CFHT). overcame.

Chandra was particularly valuable for this study because the material surrounding black holes can heat up to millions of degrees, producing large amounts of X-rays. The team looked for pairs of bright X-ray sources in dwarf galaxies colliding as evidence of two black holes and found two examples.

A pair is in the Abell 133 galaxy cluster, located 760 million light-years from Earth, as seen in the left composite image. Chandra X-ray data is in pink and CFHT optical data is in blue. This dwarf galaxy pair appears to be in the final stages of a merger and displays a long tail caused by the tidal effects of the collision. The authors of the new study nicknamed it “Mirabilis” after an endangered species of hummingbird known for its unusually long tails. Only one name was chosen, as the merger of the two galaxies was almost complete. Two Chandra sources show X-ray emission of material around black holes in each galaxy.