Scientists Just Found 300 of Some of the Rarest Black Holes in the Universe

• Intermediate-mass black holes—somewhere between stellar-mass and supermassive—are the rarest type of black hole in the universe.
• 300 of these elusive black holes were recently observed by NSF NOIRLab’s DESI (Dark Energy Spectroscopic Instrument).
• While some are the active galactic nuclei of dwarf galaxies, most are thought to have been the seeds of what are now supermassive black holes.

Some black holes are supermassive beasts up to tens of billions of times the mass of our Sun. Then, there are stellar-mass black holes, which top out at a few solar masses. So… what fills the void in between?

One of the rarest types of black holes in the universe are intermediate-mass black holes (IMBHs). Sometimes referred to as “missing link” black holes, these cosmic gaping maws—which can be anywhere from about 100 to 100,000 solar masses in size—have proved difficult to find. Recently, however, NSF NOIRLab’s Dark Energy Spectroscopic Instrument (DESI) has been able to detect 300 more of them. DESI also detected active black holes in many dwarf galaxies, which are exactly what they sound like—rather small black holes with only a handful of stars (if you could call thousands to several billion a handful) scattered around.

Related Story

Only between 100 and 150 IMBHs were known, until now. Using the new data, a research team led by Ragadeepika Pucha from the University of Utah wanted to find out what intermediate-mass black holes can tell us about black hole formation.

Supermassive black holes (SMBHs), which lurk in the centers of enormous galaxies like our own, destroy and consume so much material and expel so much energy that they are fairly obvious. Both the Milky Way’s supermassive black hole (Sagittarius A*) and the monster at the heart of the galaxy M83 were able to be imaged because of the extreme brightness of their accretion disks.

Black holes of lower mass, however, don’t devour nearly as much. As a result, they are harder to make out—though, it does help if a smaller black hole is actively feeding at the time of observation, as the energy given off as it rips stars apart makes it easier to spot.

“When a black hole at the center of a galaxy starts feeding, it unleashes a tremendous amount of energy into its surroundings, transforming into what we call an active galactic nucleus,” Pucha said in a press release. “This dramatic activity serves as a beacon, allowing us to identify hidden black holes in these small galaxies.”

While Pucha’s team was expecting most of the newly discovered IMBHs to be the active galactic nuclei (AGNs) of dwarf galaxies, that turned out not to be the case. Only 70 intermediate-mass black holes were associated with dwarf galaxies, judging by where their energy emissions came from. This is a surprise, considering how closely IMBHs are associated with dwarf galaxies (Given their size, it makes sense that their AGNs would be black holes of intermediate mass). But surprises are like candy to scientists, as they offer opportunities to ask questions that the experts may never have even thought to pose.

After finding out the remaining IMBHs were not in dwarf galaxies, the researchers want to continue investigating these mysterious objects. They think that at least some of these black holes could be supermassive black hole seeds that might help explain the origins of the SMBHs we see in the universe today.

SMBHs form by accretion, meaning that they accumulate more and more mass over time—either through standard “eating” or through mergers with other black holes—until they reach a size that can hold a galaxy together. But these gigantic black holes had to start somewhere, and one of the leading theories for what their seeds may have been is IMBHs.

Because the IMBHs observed by DESI are so distant, the team was able to see them as they were billions and billions of years ago, since that is how long their light took to reach Earth. As a result, it is possible that some of these objects have evolved into SMBHs by now, and studying their origins could tell us a lot about their evolution.

Related Stories

“As we cannot directly observe their formation with our current telescopes, we focus on their imprints on the local universe,” Pucha and her team said in a study recently posted to the preprint server arXiv. “Most of these early black holes grow via accretion and mergers into the SMBHs we see today.”

DESI, which will be scanning the sky for five more years, is expected to observe around 40 million galaxies and quasars during its lifespan. If it’s already found 300 examples of one of the universe’s greatest mysteries, who knows what else it will find.

Elizabeth Rayne is a creature who writes. Her work has appeared in Ars Technica, SYFY WIRE, Space.com, Live Science, Den of Geek, Forbidden Futures and Collective Tales. She lurks right outside New York City with her parrot, Lestat. When not writing, she can be found drawing, playing the piano or shapeshifting.

_{Images are for reference only.Images and contents gathered automatic from google or 3rd party sources.All rights on the images and contents are with their legal original owners.}