Most of the large galaxies in the universe harbor supermassive black holes at their center. Our own Milky Way has one, too, and it goes by the name of Sagittarius A — a fascinating and exotic place that may even be surrounded by a swarm of 10,000 smaller black holes, the Inquisitr previously reported.
Yet, in a rare find, astronomers have recently come across a supermassive black hole reigning the center of a tiny galaxy, Phys.org reported earlier today.
The news came from Lomonosov Moscow State University (MSU) in Russia, which published a study in the journal Monthly Notices of the Royal Astronomical Society detailing this spectacular discovery.
Dubbed UCD3, this particular galaxy lies in the Fornax cluster — a collection of galaxies located some 62 million light-years away in the Fornax constellation — and belongs to a rare class of galaxies known as ultracompact dwarfs (UCDs).
These tiny galaxies have only been discovered in the past two decades and sport very unusual features, explains study lead author Anton Afanasiev, a student at MSU’s Faculty of Physics.
“UCDs are rather compact stellar systems with typical radii of about 100 parsecs (around 326 light-years), while their masses are up to 100 million solar masses,” Afanasiev told Newsweek. “As a result, their stars exist ‘densely packed,’ with interstellar distances way shorter than in our galaxy.”
By comparison, our galaxy has a radius of about 50,000 light years and a mass of hundreds of billions of times that of the sun, notes the media outlet.
Finding a supermassive black star nestled within a UCD is a true rarity, as only three other cases have ever been described, Afanasiev and his colleagues note in their paper. Even more notably, this is the first-ever supermassive black hole reported in the Fornax cluster.
According to the researchers, an MSU-led international team from Europe, the U.S., and Australia, these dwarf galaxies are believed to have inherited the monster black holes at their center from the massive galaxies that spawned them, also known as progenitor galaxies.
“Similarly to other known UCDs that harbor black holes, UCD3 hosts metal rich stars enhanced in alpha elements that support the tidal stripping of a massive progenitor as its likely formation scenario,” the authors wrote in their paper.
Commenting on the discovery, Afanasiev explained why this origin theory holds ground.
“This hypothesis is backed by the fact that all UCDs hosting black holes are found in the central parts of galaxy clusters, where tidal stripping events are much more likely and the fraction of stars that are being ‘stolen’ by a bigger galaxy is higher. But to confidently state this we need to see some more black holes — at least 5 — in UCDs following proposed regularity.”
The intriguing thing about Fornax UCD3 is that, unlike regular galaxies where the central supermassive black holes occupy about 0.3 percent of their mass, its supermassive black hole is a mammoth taking up about 4 percent of the galaxy’s total mass. In addition, it weighs about 3.5 million solar masses — almost the same as Sagittarius A, Afanasiev pointed out.
Another noteworthy detail is that UCDs are a lot brighter than other galaxies — including the Milky Way, notes Fox News — and are typically home to older stars.
This amazing discovery was made possible with the help of the European Southern Observatory’s Very Large Telescope (VLT) in the Atacama Desert in Chile. Afanasiev’s team spotted the supermassive black hole at the heart of Fornax UCD3 after combing through data from VLT’s SINFONI instrument, an infrared integral field spectrograph that picked up the spectra of stars in Fornax UCD3, revealing their velocity dispersion.
The observations showed that the stars in the center of the galaxy had very high velocity dispersion and were “accelerating in various directions” under the influence of the mammoth’s gravitational pull, leading the team to uncover the supermassive black hole hidden within Fornax UCD3.
The researchers speculate that up to 80 percent of UCDs found in bright galaxy clusters could be harboring supermassive black holes.