Milky Way’s supermassive black hole (SMBH) may have ‘unseen’ siblings

Understanding what happens when black holes get the urge to roam the Milky Way.


A supermassive black hole (SMBH) exists at the core of a massive galaxy. But sometimes SMBHs may “wander” throughout their host galaxy, remaining far from the center in regions such as the stellar halo, a nearly spherical area of stars and gas that surrounds the main section of the galaxy.

According to astronomers, this wonder frequently happens because of mergers between cosmic systems in a growing universe. A smaller galaxy will join with a bigger, principal universe, storing its own central SMBH onto a wide circle inside the new host.

Now, astronomers started gazing at what happens when black holes get the urge to roam the Milky Way.

In a new study by scientists at Yale University in collaboration with the University of Washington, Institut d’Astrophysique de Paris, and University College London predicts that Galaxies with a mass like the Milky Way should have a few supermassive dark gaps.

Scientists used a new, state-of-the-art cosmological simulation, Romulus, to predict the dynamics of SMBHs within galaxies with better accuracy than previous simulation programs.

Lead author Michael Tremmel, a postdoctoral fellow at Yale said, “It is extremely unlikely that any wandering supermassive black hole will come close enough to our Sun to have any impact on our solar system. We estimate that a close approach of one of these wanderers that is able to affect our solar system should occur every 100 billion years or so, or nearly 10 times the age of the universe.”

“Since wandering SMBHs are predicted to exist far from the centers of galaxies and outside of galactic disks, they are unlikely to accrete more gas — making them effectively invisible. We are currently working to better quantify how we might be able to infer their presence indirectly.”

Co-authors of the study are Fabio Governato, Marta Volonteri, Andrew Pontzen, and Thomas Quinn.

The study is published in the Astrophysical Journal Letters.

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