October 4, 2023

Hungry black hole ‘turns on’ as astronomers watch in amazement

    a bright red beam of light that shoots into space in two directions

a bright red beam of light that shoots into space in two directions

One of the brightest transient events is the result of a supermassive black hole beginning to feast on surrounding matter, resulting in one of the most dramatic “turning on” events ever seen.

Transients are astronomical events or objects that change brightness in a short period of time, and the one powered by this greedy black hole – J221951 – is one of the brightest transients ever recorded. The position of the black hole corresponds to the center of a previously observed galaxy, exactly where a supermassive black hole should sit. However, astronomers are still not exactly sure what causes the transient event witnessed in J221951.

“Our understanding of the different things supermassive black holes can do has expanded enormously in recent years, with discoveries of stars being ripped apart and accreting black holes of wildly variable brightness,” said team member and astronomer from the University of Belfast, Matt Nicholl, in a position. “J221951 is one of the most extreme examples yet of a black hole that surprised us.”

Related: Star survives spaghettification by black hole

The nature of what consumes the supermassive black hole about 10 billion light-years away is currently unknown, but it is possible that J221951 represents a star that has gotten too close to the black hole and is being violently torn apart by tidal forces coming from its immense gravity in a process called spaghettification.

This event, called a tidal perturbation event (TDE), would cause some of the destroyed star’s stellar material to fall to the black hole’s surface, while other matter would be funneled to the black hole’s poles before colliding at near light. is blown out. velocities, generating intense electromagnetic radiation.

However, the spaghettification of an unlucky star isn’t the only possible mechanism that could cause the black hole in question to give rise to this bright transient event. Another possibility is that J221951 is the result of the nucleus at the heart of a galaxy switching from a dormant to an active state.

Active Galactic Nuclei (AGNs) are bright regions at the heart of galaxies that emit enough light to drown out the combined light from every star in the rest of that galaxy. They are also powered by supermassive black holes.

“Continued monitoring of J221951 to determine the total energy released could allow us to work out whether this is a tidal disturbance of a star by a rapidly spinning black hole or a new kind of AGN switch,” Nicholl added. .

Watching the dramatic “turn on” at the heart of a galaxy

Kilonovas are a type of transient event that occurs during the merger of two neutron stars or a neutron star and a black hole, releasing bright bursts of electromagnetic radiation. Kilonovas are initially blue in color and then fade to red over a period of a few days. The transient J221951 also appeared blue, but it didn’t turn red or fade quickly like a kilonova would. The nature of this transient was determined by follow-ups with space-based facilities like the Hubble Space Telescope and ground-based observatories like the Very Large Telescope (VLT) in the Atacama Desert in northern Chile.

“The most significant discovery was when Hubble’s ultraviolet (UV) spectrum ruled out a galactic origin. This shows the importance of maintaining a space-based UV spectrograph in the future,” said team member and Mullard Space Science Laboratory of University College So says the London researcher Paul Kuin.

With a source 10 billion light-years away, the team realized that J221951 must be one of the brightest events ever. They will now work to better understand its cause.


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“In the future, we will be able to obtain important clues that help distinguish between the tidal disturbance and active galactic core scenarios,” Oates said. “For example, if J221951 is associated with an AGN turning on, we would expect it to stop fading and increase in brightness again, while if J221951 is a tidal disturbance, we would expect it to continue fading.

“We will have to continue to monitor J221951 over the coming months to years to record its late behavior.”

The team presented their findings on Tuesday, July 4, at the 2023 National Astronomy Meeting in Cardiff, UK

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