The universe is teeming with black holes, ranging from supermassive behemoths at the centers of galaxies to smaller ones formed from the collapse of stars. However, the search for a “middleweight” black hole has, until now, been unsuccessful.
Astronomers announced on Wednesday that they have discovered the most compelling evidence yet for such a missing link in Omega Centauri, the Milky Way’s largest star cluster, located regarding 18,000 light-years from Earth.
They observed “something peculiar” at the heart of this cluster, which contains millions of stars, Maximilian Häberle, a doctoral student at the German Max Planck Institute for Astronomy, told AFP.
AFP
Seven stars were moving abnormally fast compared to their neighbors, a speed that should have caused them to leave the cluster. However, they seemed to be held back by the gravitational pull of an unseen, massive object.
Calculations simulating the movement of these seven stars revealed a black hole at the core of Omega Centauri, with a mass equivalent to 8,200 Suns.
This aligns perfectly with what would be considered an intermediate black hole. A stellar black hole can have a mass of up to approximately 150 solar masses, while a supermassive black hole easily exceeds 100,000 solar masses. For instance, Sagittarius A*, located at the Milky Way’s center, has a mass four million times that of the Sun.
AFP
This leaves “a vast expanse” between these two extremes for intermediate black holes, noted Maximilian Häberle, lead author of the study published in Nature. And there have been very few candidates to represent them.
Black holes are impossible to detect directly, as even light cannot escape their gravitational pull. Intermediate black holes are even harder to spot because they absorb minimal surrounding matter, resulting in less light emission at this time.
Maximilian Häberle hopes this discovery will settle two decades of debate among astronomers regarding whether Omega Centauri harbors an intermediate black hole.
The team analyzed 20 years of Hubble observations to determine the motion of 1.4 million stars in Omega Centauri. They were able to rule out scenarios involving multiple stellar black holes or binary star systems, Häberle stated.
Definitive confirmation of the existence of the intermediate black hole would require directly observing the motion of stars orbiting it, which would take several hundred years, he added.
Several astronomers outside the study have called this the best evidence so far for the existence of intermediate black holes.
“This finding opens up new possibilities in understanding how common such black holes are,” Jenny Greene, an astrophysicist at Princeton University, told AFP. She suggests they might be at least as common as supermassive black holes, and potentially even five times more common.
The study of these enigmatic objects should also shed light on how black holes gain mass. One theory postulates that black holes merge with each other.
However, this doesn’t explain the recent discovery of supermassive black holes only a few hundred million years following the Big Bang, in the early Universe, using the James Webb telescope.
Stellar black holes wouldn’t have had enough time to merge in significant numbers to give rise to these behemoths.
Astronomers are looking forward to the anticipated launch in 2028 of the ELT (Extremely Large Telescope), the largest telescope in the world, to further investigate both medium and heavy black holes.
Astronomers Finally Detect a Mid-Sized Black Hole
The universe teems with black holes, from the supermassive behemoths residing at the centers of galaxies to the lightweight ones born from the collapse of stars. However, the search for a “middleweight” black hole has remained elusive until now. Astronomers have announced the discovery of the best evidence yet for this missing link, located within Omega Centauri, the largest star cluster in the Milky Way, approximately 18,000 light-years from Earth.
Unveiling the Hidden Giant
Researchers noticed a peculiar anomaly at the heart of Omega Centauri, a cluster harboring an estimated ten million stars. Maximilian Häberle, a doctoral student at the German Max Planck Institute for Astronomy, described it as “something curious.” Seven stars were observed moving at an exceptionally fast pace compared to their counterparts, defying the expectation that they should have been ejected from the cluster. Their persistence suggested a powerful gravitational force holding them captive, invisible yet undeniably present.
Calculations simulating the motion of these seven stars revealed the presence of a black hole, nestled within the core of Omega Centauri, and boasting a mass equivalent to 8,200 suns. This discovery marks the long-sought intermediate black hole, a category bridging the gap between the more familiar stellar black holes and the supermassive behemoths that dominate galactic centers.
Bridging the Gap in Black Hole Sizes
Stellar black holes have a maximum mass of approximately 150 solar masses, whereas supermassive black holes easily surpass 100,000 solar masses. Sagittarius A*, sitting at the Milky Way’s heart, boasts a mass four million times that of our sun.
The newly discovered black hole fills a critical void between these two extremes, highlighting a previously underappreciated population of black holes. The absence of substantial matter absorption by these intermediate black holes makes them remarkably difficult to detect, as they emit minimal light.
A 20-Year Enigma Solved
Maximilian Häberle, lead author of the study published in Nature, expressed hope that this discovery will finally resolve two decades of debate among astronomers regarding the existence of an intermediate black hole within Omega Centauri. His team meticulously examined 20 years of Hubble Telescope observations, focusing on the movement of 1.4 million stars within the cluster.
Through this analysis, they effectively eliminated alternative explanations, such as multiple stellar black holes or binary star systems. However, obtaining definitive confirmation of this intermediate black hole requires directly observing the motion of stars orbiting it, a process that might take hundreds of years, according to Häberle.
Implications for Understanding Black Hole Formation
Several astronomers, unconnected to the study, have hailed this discovery as the most compelling evidence yet for the existence of intermediate black holes. Jenny Greene, an astrophysicist at Princeton University, emphasizes the potential for understanding how common these black holes might be, suggesting they might be as prevalent as supermassive black holes, possibly even five times more common.
This discovery has significant implications for comprehending black hole mass growth. One prevailing theory proposes that black holes merge with each other. However, this theory struggles to explain the recent detection of supermassive black holes by the James Webb Telescope, located just a few hundred million years following the Big Bang, during the early stages of the universe.
The short timeframe suggests that stellar black holes wouldn’t have had sufficient time to merge in substantial numbers, creating the observed supermassive behemoths. Astronomers are now placing their hopes on the upcoming launch of the ELT (Extremely Large Telescope) in 2028. ELT, expected to become the world’s largest telescope, holds the promise of advancing our understanding of both intermediate and supermassive black holes.
Key Findings
Here are some key takeaways from the discovery of the intermediate black hole within Omega Centauri:
* The most compelling evidence yet for the existence of intermediate black holes.
* The black hole’s mass is equivalent to 8,200 suns, filling a gap between stellar and supermassive black holes.
* Suggests intermediate black holes might be as common as supermassive black holes, possibly even more common.
* This discovery challenges existing theories on black hole growth, particularly regarding supermassive black holes in the early universe.
* The upcoming launch of the ELT presents a prime opportunity to further explore the characteristics and distribution of intermediate and supermassive black holes.
As the search for knowledge regarding the universe continues, this groundbreaking discovery promises to push the boundaries of our understanding of black holes and their profound influence on the cosmos.
