When a star hits a black hole, it has little chance of escaping unscathed. It is even a rather tragic ending that awaits him. Like the ones astronomers have just observed. The story of an unfortunate star turned from a black hole into a cosmic donut.
Flirting with a black hole is not advisable. Because even if he is not the flirtatious hunter type, the black hole never rejects the advances of a beautiful young lady who offers herself to him. So when a star approaches, it is quickly trapped by the black hole’s gravity and cannot move back. It then goes through what astronomers call a tidal break event. The star is literally torn apart and then swallowed up by the black hole. And the monster then “spits out” intense radiation. A bit like belching after a hearty cosmic meal.
Astronomers have observed a star being “spaghettified” by a black hole
Over the years, astronomers using various instruments have been able to observe around a hundred of these tidal breaks. But the one NASA researchers are talking about today is special. Because it was observed in the ultraviolet range, “a range that can teach us a lot”. While most tidal break events are still observed in X-rays.
It was the first All-Sky Automated Survey for Supernovae – whose mission is precisely to monitor the sky in search of transient events – which detected the characteristic burp of tidal breaks in March 2021. A high-energy burst of radiation emanating from the core of a galaxy named ESO 583-G004. Its relative proximity – the event occurred about 300 million light-years from Earth – and its intensity allowed NASA astronomers to study it with the ultraviolet spectrograph equipped with the Hubble Space Telescope.
New view of a black hole meal
While tidal break events are usually studied primarily when they are triggered when they are very bright, the researchers here were able to observe AT2022dsb fairly early in its history and over a much longer period of time. Because the team’s idea is to observe the tide break events over a whole year. What a great way to see the accretion rate evolution – understand the speed at which the star is being engulfed by the supermassive black hole. And then compare the model predictions to these new observations.
This time, therefore, astronomers observed how the rate of accretion slowed down until the black hole looked like a strange bird collecting crumbs. And they’re interpreting today’s Hubble spectroscopic data as coming from a region of gas that’s very bright, hot, and… ring-shaped. The remnant of what was once a star. A region the size of our solar system that swirls around the black hole.
At the edge of this donut, the astronomers were collecting data “in an exciting place, on the border between what we know and what we don’t know.” Enough to already allow them to confirm that black holes feed a bit like pigs. With stellar debris ejected by stellar winds. These sweep across the surface of the cosmic donut at breakneck speed. About 30 million kilometers per hour or about 3% of the speed of light.