Black Hole Devours Star, Triggering Energy Burst That Could Have Outshone Galaxy

Astronomers have investigated a powerful burst of energy, discovering that it came from a black hole devouring a star.

The event is of particular interest because the feasting black hole is a type of object that has thus far proved elusive to astronomers, an intermediate-mass black hole.

An intermediate mass black hole is a black hole with a mass of between 100 and 10,000 times that of the sun. Lying between smaller stellar mass black holes and gigantic supermassive black holes, they have remained difficult to spot as, like all black holes, they don't emit light light.

Intermediate-mass black holes have long been believed to exist by scientists, but were missing from observations until the first example was spotted last year from the tiny ripples in space, or gravitational waves, that the merger that created it caused.

This newly observed "feeding," which is more accurately called a tidal disruption event, created a powerful burst of energy that not only made this black hole visible to astronomers, but also allowed them to learn more about the black hole that sparked it.

As the stars in these tidal disruption events are ripped apart, or "spaghettified," and disappear into the black holes, they can create flares so powerful that they outshine the emissions of every star in the galaxies in which they occur. This can often last for a period of months or even years.

The researchers, led by University of Arizona Steward Observatory postdoctoral research associate Sixiang Wen, used X-rays from the J2150 tidal disruption event to make measurements of the black hole's mass and the rate at which it spins. A paper documenting the research was published in The Astrophysical Journal.

The team said that the devouring black hole in question is 10,000 times the mass of the sun, which makes it too small to be a supermassive black and too large to be a stellar-mass black hole.

"The fact that we were able to catch this black hole while it was devouring a star offers a remarkable opportunity to observe what otherwise would be invisible," co-author and University of Arizona professor of astronomy Ann Zabludoff said in a press release.

"Not only that, by analyzing the flare we were able to better understand this elusive category of black holes, which may well account for the majority of black holes in the centers of galaxies."

Black Hole eats Star
A simulation of a tidal disruption event that occurs when a star comes too close to a black hole. The energy emissions of such events could outshine entire galaxies. Chris Smith USRA/GESTAR/NASA Goddard Space Flight Center

Astronomers have spotted feasting black holes before, but these observations have usually been limited to the supermassive black holes that lurk at the center of larger galaxies like our own. None have been confirmed to be the result of tidal events with an intermediate-mass black hole, which could dwell at the center of galaxies that are much smaller than the Milky Way.

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

Not only could this research teach scientists more about these elusive intermediate black holes, which have masses between 100 and 1000 times that of the sun, it could also help them understand more about how black holes grow to supermassive status.

Co-author Peter Jonker of Radboud University and SRON Netherlands Institute for Space Research said that despite how common they are, we still don't know how supermassive black holes get so massive.

The collapse of a single star could never create something as big as even an intermediate-mass black hole, but these elusive stellar remnants could form from mergers and become the seeds for further mergers which create the most massive black holes.

"We still know very little about the existence of black holes in the centers of galaxies smaller than the Milky Way. Due to observational limitations, it is challenging to discover central black holes much smaller than 1 million solar masses," Jonker said. "Therefore, if we get a better handle of how many bona fide intermediate black holes are out there, it can help determine which theories of supermassive black hole formation are correct."

The key to understanding this growth mechanism, the team said, may lie not in the measurement of the black hole's mass, but in the observation of its rate of spin. The researchers discovered that the intermediate mass black hole was spinning quickly, but not at the fastest possible rate.

"It's possible that the black hole formed that way and hasn't changed much since, or that two intermediate-mass black holes merged recently to form this one," Zabludoff said. "We do know that the spin we measured excludes scenarios where the black hole grows over a long time from steadily eating gas or from many quick gas snacks that arrive from random directions."

The team's research could have significance beyond black holes, however.

Dark matter is a mysterious substance that makes up around 80 percent of the Universe's matter content. Researchers know little about it other than it doesn't interact with light or matter like the radiation matter that makes up stars, planets, and us does.

Dark matter can only really been seen through the interactions it has with gravity, which prevent the galaxies themselves from flying apart. The team at the center of this research believes that the spin of this black hole could give clues as to what dark matter is made up of by eliminating some of the possible particles as candidates. In particular, it could rule out hypothetical particles called ultralight bosons.

"If those particles exist and have masses in a certain range, they will prevent an intermediate-mass black hole from having a fast spin," Stone said. "Yet J2150's black hole is spinning fast. So, our spin measurement rules out a broad class of ultralight boson theories, showcasing the value of black holes as extraterrestrial laboratories for particle physics."

Before any further investigations into either black holes or dark matter can be conducted, however, the team says that more intermediete-mass black holes must be discovered.

The hope is that telescopes like the James Webb Space Telescope and the Vera C. Rubin Observatory, set to begin operations over the next few years, will be able to contribute to this search.

"By fitting the X-ray emission from these flares to theoretical models, we can conduct a census of the intermediate-mass black hole population in the universe," Wen said.

A Black Hole Consumes a Star
A stock illustration shows a jet of material torn apart and consumed by a black hole. Researchers have used powerful emissions created as a black hole devoured a star to measure its mass and spin. JPL-Caltech/NASA