Supermassive black holes discovered to outgrow host galaxies

Astronomers have identified eight supermassive black holes that significantly outweigh their host galaxies, challenging long-held cosmological assumptions about how these celestial bodies evolve. Traditionally, scientists believed that black holes and their host galaxies grow in tandem, with the central black hole typically accounting for approximately 0.5 percent of the galaxy's mass, a ratio of roughly 1:200.

Using data from the eROSITA X-ray telescope aboard the Spektr-RG space observatory, a research team led by the Max Planck Institute for Extraterrestrial Physics analyzed over 20,000 quasars. They discovered eight systems where the black hole-to-galaxy mass ratio is at least 5 percent, or 1:20. This is more than ten times the standard expected ratio.

The black holes in these anomalous systems range from 800 million to four billion solar masses. The findings, published in Astronomy & Astrophysics, suggest that the growth of central black holes is not always closely coupled to the development of their host galaxies, contradicting several leading cosmological computer simulations.