Tour: NASA Telescopes Pinpoint Free-Roaming Massive Black Hole

Astronomers have discovered a black hole has torn apart a star in a surprising location. When an unlucky star strays too close to a giant black hole and gets destroyed, scientists call these tidal disruption events, or TDEs. This particular TDE is unusual because it did not happen at the center of the galaxy where supermassive black holes are generally found. Instead, it occurred about 2,600 light-years away from the supermassive black hole in the center of the galaxy. This suggests this galaxy, located about 600 million light-years from Earth, has a second giant black hole lurking within it.

A TDE happens when an infalling star is stretched or “spaghettified” by a black hole’s immense gravitational tidal forces. The shredded stellar remnants are pulled into a circular orbit around the black hole. This generates shocks and outflows with high temperatures that can be seen in ultraviolet and visible light. X-rays are produced when material from the destroyed star falls toward the black hole and is heated to millions of degrees.

The new TDE is called AT2024tvd and to determine its exact location within the galaxy, researchers turned to some of the best telescopes in different kinds of light including NASA's Hubble Space Telescope and Chandra X-ray Observatory and the NSF's Karl G. Jansky Very Large Array, or VLA. Chandra is the only X-ray telescope with vision sharp enough to distinguish between the offset TDE and the center of the galaxy.

Based on what they observed, the team estimates that the supermassive black hole responsible for the TDE has a mass of about a million Suns. This is large, but smaller than the black hole they think exists in the center of the galaxy that about 100 times more massive.

How did the black hole get off-center? Scientists have created models that show that black holes can be ejected out of the centers of galaxies when a supermassive black hole encounters a pair of supermassive black holes. Under the right conditions, the lowest-mass member in this scenario gets kicked out. This may be the case here, given the stealthy black hole’s close proximity to the central black hole. An alternative explanation is that the black hole is the surviving remnant of a smaller galaxy that merged with the host galaxy more than 1 billion years ago.

While scientists continue to get to the bottom of things with AT2024tvd, they will keep looking for other examples of TDEs like it. Chandra, Hubble, and these other telescopes online will soon be joined by other facilities like the Vera C. Rubin Observatory in Chile and the Roman Space Telescope that will help investigate mysteries like these.