When Suns Meet Black Holes: Astronomers Spot 18 Instances

Astronomers spot 18 black holes gobbling up nearby stars in a new study that more than doubles the number of known tidal disruption events in the universe.

Star-shredding black holes are everywhere in the sky if you just know how to look for them. That’s one message from a new study by MIT scientists, appearing today in the Astrophysical Journal. The study’s authors are reporting the discovery of 18 new tidal disruption events (TDEs) — extreme instances when a nearby star is tidally drawn into a black hole and ripped to shreds. As the black hole feasts, it gives off an enormous burst of energy across the electromagnetic spectrum.

Infrared detection

Astronomers have detected previous tidal disruption events by looking for characteristic bursts in the optical and X-ray bands. To date, these searches have revealed about a dozen star-shredding events in the nearby universe. The MIT team’s new TDEs more than double the catalog of known TDEs in the universe.

The researchers spotted these previously “hidden” events by looking in an unconventional band: infrared. In addition to giving off optical and X-ray bursts, TDEs can generate infrared radiation, particularly in “dusty” galaxies, where a central black hole is enshrouded with galactic debris. The dust in these galaxies normally absorbs and obscures optical and X-ray light, and any sign of TDEs in these bands. In the process, the dust also heats up, producing infrared radiation that is detectable.

The team found that infrared emissions, therefore, can serve as a sign of tidal disruption events. By looking in the infrared band, the MIT team picked out many more TDEs, in galaxies where such events were previously hidden. The 18 new events occurred in different types of galaxies, scattered across the sky.

“The majority of these sources don’t show up in optical bands,” says lead author Megan Masterson, a graduate student in MIT’s Kavli Institute for Astrophysics and Space Research. “If you want to understand TDEs as a whole and use them to probe supermassive black hole demographics, you need to look in the infrared band.”

Implications and future work

The new detections have implications for understanding how supermassive black holes grow and evolve over time. TDEs are thought to be one of the main ways that black holes can accrete mass and energy from their surroundings. By observing more TDEs, astronomers can estimate how often these events occur and how they affect black hole growth.

The team also plans to use their infrared-based method to search for more TDEs in larger surveys of the sky, such as those conducted by NASA’s Wide-field Infrared Survey Explorer (WISE) and the upcoming Vera C. Rubin Observatory. They hope to find hundreds or even thousands of new star-shredding events that can reveal more about the nature and diversity of black holes.

Other MIT authors include Kishalay De, Christos Panagiotou, Anna-Christina Eilers, Danielle Frostig, and Robert Simcoe, and MIT assistant professor of physics Erin Kara, along with collaborators from multiple institutions including the Max Planck Institute for Extraterrestrial Physics in Germany.

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