This is what it looks like when a black hole nibbles at a star

While black holes and toddlers don’t seem to have much in common, they are remarkably similar in one aspect – both are messy eaters, generating plenty of evidence that a meal has taken place.

But while one may leave behind pasta feces or splash of yogurt, the other creates a sequel of mind-boggling proportions. When a black hole engulfs a star, it produces what astronomers call a “tidal disturbance event.” With the shredding of the hapless star comes an explosion of radiation that can eclipse the combined light from each star in the black hole’s host galaxy for months, if not years.

In an article published in The Journal of Astrophysics, a team of astronomers led by Sixiang Wen, a postdoctoral research associate at the University of Arizona’s Steward Observatory, use x-rays emitted by a tidal disturbance event known as J2150 to perform the first measurements of the mass and rotation of the black hole. This black hole is of a special type – a black hole of intermediate mass – which has long escaped observation.

“The fact that we were able to catch this black hole as it devoured a star provides a remarkable opportunity to observe what would otherwise be invisible,” said Ann Zabludoff, UArizona professor of astronomy and co-author of the article. “Not only that, by analyzing the eruption, we were able to better understand this elusive category of black holes, which may well represent the majority of black holes in the center of galaxies.”

By re-analyzing the x-ray data used to observe the J2150 eruption, and comparing them to sophisticated theoretical models, the authors showed that this eruption did indeed come from an encounter between an unlucky star and a mass black hole. intermediate. The intermediate black hole in question is of particularly low mass – for a black hole, that is – weighing about 10,000 times the mass of the sun.

“X-ray emissions from the inner disk formed by the debris of the dead star allowed us to deduce the mass and spin of this black hole and classify it as an intermediate black hole,” Wen said.

Dozens of tidal disturbance events have been observed in the centers of large galaxies hosting supermassive black holes, and a handful have also been observed in the centers of small galaxies that may contain intermediate black holes. However, past data has never been detailed enough to prove that an individual tidal disturbance eruption was fueled by an intermediate black hole.

“From modern astronomical observations, we know that the centers of almost all galaxies that are similar in size to or larger than our Milky Way host central supermassive black holes,” said study co-author Nicholas Stone, lecturer at the Hebrew University of Jerusalem. “These behemoths are between 1 million and 10 billion times the mass of our sun, and they become powerful sources of electromagnetic radiation when too much interstellar gas falls in their vicinity.”

The mass of these black holes is closely related to the total mass of their host galaxies; the largest galaxies are home to the largest supermassive black holes.

“We still know very little about the existence of black holes at the center of galaxies smaller than the Milky Way,” said co-author Peter Jonker of Radboud University and SRON Netherlands Institute for Space Research, all two in the Netherlands. “Due to observation limitations, it is difficult to find central black holes much smaller than a million solar masses.”

Despite their presumed abundance, the origins of supermassive black holes remain unknown, and many different theories currently compete to explain them, according to Jonker. Intermediate mass black holes could be the seeds from which supermassive black holes develop.

“Therefore, if we get a better idea of ​​the number of bona fide intermediate black holes, it can help determine which theories of supermassive black hole formation are correct,” he said.

Even more exciting, according to Zabludoff, is the measure of the J2150’s spin the group was able to achieve. The spin measurement contains clues about the growth of black holes and possibly particle physics.

This black hole has a fast spinning, but not the fastest spinning possible, Zabludoff explained, asking how the black hole ends up with a spin in this range.

“It’s possible that the black hole formed this way and hasn’t changed much since, or that two black holes of intermediate mass have recently merged to form this one,” she said. “We know that the rotation we measured excludes scenarios in which the black hole grows over a long period of time due to constant gas consumption or many quick snacks on gas arriving from random directions.”

Additionally, measuring spin allows astrophysicists to test hypotheses about the nature of dark matter, which is believed to make up most of the matter in the universe. Dark matter can be made up of unknown elementary particles that have not yet been seen in laboratory experiments. Among the candidates are hypothetical particles known as ultralight bosons, Stone explained.

“If these particles exist and have masses within a certain range, they will prevent a black hole of intermediate mass from spinning rapidly,” he said. “Yet the J2150 black hole is spinning rapidly. So our spin measurement excludes a large class of ultralight boson theories, showing the value of black holes as alien laboratories for particle physics.”

In the future, new observations of tidal disturbance eruptions could allow astronomers to fill gaps in the mass distribution of black holes, the authors hope.

“If it turns out that most dwarf galaxies contain intermediate mass black holes, then they will dominate the rate of stellar tidal disturbance,” Stone said. “By adapting the X-ray emission from these flares to theoretical models, we can perform a population census of intermediate mass black holes in the universe,” Wen added.

To do this, however, more tidal disturbance events need to be observed. That’s why astronomers have high hopes that new telescopes will soon come online, both on Earth and in space, including the Vera C. Rubin Observatory, also known as the Legacy Survey of Space and Time, or LSST, which is expected to uncover thousands of tidal disruptive events per year.