BBC Sky at Night Magazine

Dinner time for black holes

An orbiting star is shown to be keeping a black hole on a regular snack schedule

Astronomer­s think they know when to next ring a black hole’s dinner bell, after they accurately predicted when the supermassi­ve giant would snack on a nearby star.

The black hole, which is 50 million times the mass of our Sun and located in a galaxy about 860 million lightyears from Earth, first became of interest when it suddenly brightened in 2018. Follow-up observatio­ns determined the surge was due to a tidal disruption event, when a passing star is torn apart and consumed by a black hole. The gas is heated as it’s pulled in, releasing more X-ray and ultraviole­t radiation which then

suddenly falls away when the gas is consumed by the black hole. When this happened after the 2018 event, astronomer­s assumed the star had been swallowed whole. Then two years later, a second brightenin­g occurred – the star had lived to die another day.

Researcher­s predicted a third brightenin­g, which they then observed in August 2023.

“Our data show that in August last year, the black hole was essentiall­y wiping its mouth and pushing back from the table,” says Dheeraj Pasham of the Massachuse­tts Institute of Technology, who led a new paper predicting when the next meal will occur.

“We think that a third meal by the black hole, if anything is left of the star, will begin between May and August of 2025 and last for almost two years,” says Eric Coughlin from Syracuse University, New York, who also took part in the study.

“This will probably be more of a snack than a full meal, because the second meal was smaller than the first, and the star is being whittled away.” www.chandra.si.edu