Scientists hunt for the 2nd-closest supermassive black hole near Earth

tech.hindustantimes.com:

Two astrophysicists at the Center for Astrophysics Harvard & Smithsonian have suggested a way to observe what could be the second-closest supermassive black hole to Earth: a behemoth 3 million times the mass of the Sun, hosted by the dwarf galaxy Leo I.

The supermassive black hole, labeled Leo I*, was first proposed by an independent team of astronomers in late 2021. The team noticed stars picking up speed as they approached the center of the galaxy -- evidence for a black hole but directly imaging emission from the black hole was not possible.

Now, CfA astrophysicists Fabio Pacucci and Avi Loeb suggest a new way to verify the supermassive black hole's existence; their work is described in a study published today in the Astrophysical Journal Letters.

"Black holes are very elusive objects, and sometimes they enjoy playing hide-and-seek with us," says Fabio Pacucci, lead author of the ApJ Letters study. "Rays of light cannot escape their event horizons, but the environment around them can be extremely bright -- if enough material falls into their gravitational well. But if a black hole is not accreting mass, instead, it emits no light and becomes impossible to find with our telescopes."

This is the challenge with Leo I -- a dwarf galaxy so devoid of gas available to accrete that it is often described as a "fossil." So, shall we relinquish any hope of observing it? Perhaps not, the astronomers say.

"In our study, we suggested that a small amount of mass lost from stars wandering around the black hole could provide the accretion rate needed to observe it," Pacucci explains. "Old stars become very big and red -- we call them red giant stars. Red giants typically have strong winds that carry a fraction of their mass to the