A midsize black hole is discovered as it 'gobbled up' a star in a dwarf galaxy

A mid-sized black hole lurking undetected in a dwarf galaxy revealed itself to astronomers when it gobbled up an unlucky star that strayed too close, according to a new study published today (Nov .10) in Nature Astronomy.

The discovery made it possible to determine the black hole's mass. It could also help scientists better comprehend how black holes and galaxies interact.

Mass of the black hole "pinned down" thanks to YSE data

The star's destruction, known as a "tidal disruption event" or TDE, resulted in a flare of radiation that briefly eclipsed the dwarf galaxy's total stellar brightness. This dwarf galaxy is known as j152120.07+140410.5, and is 850 million light-years away.

The astronomers captured the flare with the Young Supernova Experiment (YSE)- an international survey designed to detect cosmic explosions and transient astrophysical events.

They spotted the first hints of light when the black hole started devouring the star, thanks to information from YSE. The time of these events helps to calculate the mass of the black hole's center. Therefore capturing this initial moment was crucial to understanding how huge the black hole was.

Then, the scientists used NASA's Hubble space telescope to look at the aftereffect know as 2020neh.  As seen in the image, the ultraviolet camera on Hubble's spacecraft observed a ring of stars forming around the galaxy's nucleus.

"This flare was incredibly fast"

Ramirez-Ruiz and coauthor Brenna Mockler from UC Santa Cruz were the first to suggest this approach, which up until this point had only been demonstrated to be effective for supermassive black holes.

"This flare was incredibly fast, but because our YSE data gave us so much early information about the event, we were really able to pin down the mass of the black hole using it," said first author Charlotte Angus in a press release. Still, this figure is yet to be revealed.

Black holes in the centers of dwarf galaxies are frequently invisible to traditional black hole hunting techniques, which look for actively feeding black holes. As a result, it is only known that a tiny percentage of dwarf galaxies contain intermediate-mass black holes.

"We can use the properties of the flare itself to better understand this elusive group of middle-weight black holes"

The discovery has created widespread excitement because tidal disruption events also aid in finding more intermediate-mass black holes in quiet dwarf galaxies, explained coauthor Ryan Foley who helped plan the YSE survey.

Furthermore, according to first author Charlotte Angus of the Niels Bohr Institute, the team's findings could serve as a baseline for future research on midsize black holes.

"We can use the properties of the flare itself to better understand this elusive group of middle-weight black holes, which could account for the majority of black holes in the centers of galaxies," explained Angus.

Could gobbling up stars and dwarf galaxies be the key to black hole 'super' growth?

All giant galaxies, including the Milky Way, have supermassive black holes at their centers. These enormous monsters, with masses millions or billions of times more than that of the sun, may have developed from smaller "intermediate-mass" black holes with masses of tens of thousands to millions of solar masses.

According to one theory, the early cosmos was filled with several small dwarf galaxies that contained intermediate-mass black holes. These dwarf galaxies would have merged or been swallowed up by larger galaxies over time, with each merger increasing the mass of the galaxy's center. In the end, this merger process produced the supermassive black holes that we see today.

How supermassive black holes form is one of the biggest unanswered mysteries in astronomy

"One of the biggest open questions in astronomy is currently how supermassive black holes form," said coauthor Vivienne Baldassare, professor of physics and astronomy at Washington State University.

The question of how supermassive black holes emerge might be resolved if more midsize black holes with tidal disruption events are discovered. This study may have brought us a little bit closer.

This study was based on data from worldwide observatories, including the W. M. Keck Observatory in Hawaii, the Nordic Optical Telescope, UC's Lick Observatory, NASA's Hubble Space Telescope, the international Gemini Observatory, the Palomar Observatory, and the Pan-STARRS Survey at Haleakala Observatory.