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Our Galaxy’s Black Hole Is Not As Deadly As First Thought

A study published in Monthly Notices of the Royal Astronomical Society has indicated that, contrary to past theories, supermassive black holes are not responsible for starving their host galaxies to death.

Led by Macquarie University PhD candidate Michael Cowley, the researchers concluded that it’s unlikely that the Milky Way’s supermassive black hole is starving our galaxy of its precious star-forming fuel supply. “This work has the potential to rewrite our understanding of how the Milky Way and similar galaxies form and evolve over cosmic time,” Cowley said.

“It also spells good news for us as inhabitants within the Milky Way given it, like most massive galaxies, contains a supermassive black hole within – which may no longer be considered as significant a threat as previously thought.”

Over the past decade numerous studies have investigated how supermassive black holes may impact their host galaxies. The consensus has been that blazing energy from the black holes can doom embryonic stars before they are even born. The remaining stars then age and die, but are never replaced, which leads to the death of the galaxy.

However, these past studies tended to investigate only nearby or massive galaxies that host supermassive black holes, or were limited to a particular observational wavelength such as X-ray observations.

In the new study, the researchers observed galaxies that are growing up to look like the Milky Way, and used multi-wavelength catalogues that span 12 billion years to probe more than 90% of the age of the universe. Their findings suggest that black holes are not shutting down star formation to the extent that has been previously assumed, and that other causes may be to blame.

Cowley suggests that these findings relate to the Milky Way’s supermassive black hole, as it may become active in the future. “Currently, the Milky Way has an abnormally diminutive supermassive black hole that doesn’t output much energy,” Cowley said. “However, we expect our galaxy to merge with our neighbouring Andromeda galaxy in a few billion years or so. This merging of galaxies may provide the perfect setting to trigger our dormant black hole to grow.

“If we are correct in our theory, the merged galaxies will live in harmony. If not, the triggered black hole could spell their doom.”