The discovery of a massive black hole in the universe has been made possible through the bending of light. As light veers around an invisible mass, it reveals the presence of this colossal entity, which happens to be one of the largest black holes yet detected.
Located at the heart of a galaxy in the Abell 1201 massive cluster, approximately 2.7 billion light-years away, this ultramassive black hole is a cosmic force to be reckoned with. Its sheer size is nothing short of astounding, surpassing even supermassive black holes and weighing in at a staggering 32.7 billion times the mass of the Sun.
What makes this discovery even more remarkable is that it exceeds previous estimates by at least 7 billion solar masses. This remarkable feat has been made possible through the precise measurement of masses using curved light. By leveraging this powerful tool, researchers have been able to uncover the existence of this colossal black hole and shed new light on the mysteries of the universe.
“This particular black hole, which is roughly 30 billion times the mass of our Sun, is one of the biggest ever detected and on the upper limit of how large we believe black holes can theoretically become, so it is an extremely exciting discovery,” explains physicist James Nightingale of Durham University in the UK.
Although black holes are plentiful in the universe, they are not always easy to detect. Unless they are actively accreting material, which generates a significant amount of light as the matter heats up before being consumed by the black hole, they remain hidden from view. In fact, black holes emit no detectable light themselves, forcing us to rely on indirect methods to locate them.
One such approach involves observing the impact that black holes have on surrounding matter. As black holes exert a gravitational pull on their surroundings, they can cause stars and gas to orbit around them at high speeds, generating distinctive patterns of motion that can be detected by astronomers. In some cases, black holes can also cause visible distortions in the fabric of spacetime, known as gravitational lensing, which can be used to infer their presence.
Despite the challenges of detecting black holes, astronomers have made significant progress in recent years, using a combination of techniques to uncover their existence and better understand their role in shaping the cosmos. From supermassive black holes at the centers of galaxies to small, stellar-mass black holes scattered throughout the universe, these mysterious entities continue to captivate scientists and inspire new discoveries.
Diagram illustrating gravitational lensing. (NASA, ESA & L. Calçada)
One way we can find these black holes is looking for an effect called gravitational lensing. This occurs when space-time itself is warped by mass; imagine space-time as a rubber sheet, and the mass as a heavy weight on it. Any light traveling through that region of space-time has to travel along a curved path, and that can look very interesting to an observer watching from afar.
When light passes through a gravitational lens, it can become warped, stretched, and even magnified, resulting in distorted images of objects in the background, such as distant galaxies. This phenomenon, known as gravitational lensing, can occur on a small scale, such as when a stellar-mass black hole acts as the lens, or on a larger scale, like a cluster of galaxies. Through the study of this warped light, astronomers can gain valuable insights into the properties of the lensing mass.
In the case of Abell 1201, the brightest cluster galaxy (BCG) at its center is a well-known strong gravitational lens. This large, diffuse elliptical galaxy serves as the lensing mass, causing a galaxy located far beyond it to appear as an elongated smear, tightly wrapped around the outskirts of the BCG like an eyebrow.
The discovery of this elongated smear was made in 2003, and in 2017, astronomers made another significant discovery: a second, fainter smear located even closer to the galactic center. This finding provides further evidence of the powerful gravitational lensing effect of the BCG and offers new opportunities for studying the properties of this massive lensing mass. As astronomers continue to probe the mysteries of the universe, gravitational lensing will undoubtedly remain a valuable tool for unlocking its secrets.
Multi Unit Spectroscopic Explorer of Abell 1201 BCG, clearly showing the lensed galaxy around as a smear in the top right quadrant. (Smith et al., MNRAS, 2017)
Astronomers had previously proposed the existence of a very large black hole at the center of the BCG, based on the observed gravitational lensing effect. However, the available data was not detailed enough to resolve the central mass or provide further insights into its properties.
In more recent times, Nightingale and his colleagues were able to access more detailed observations and developed the necessary tools to analyze them. To better understand the gravitational lensing effect observed in Abell 1021 BCG, they conducted hundreds of thousands of simulations of light moving through the Universe. They varied the mass of the black hole at the center of the BCG, searching for models that best replicated the observed lensing.
Remarkably, all but one of their simulations favored the presence of a massive black hole at the center of the galaxy. The best-fit model suggested a black hole with a mass of 32.7 billion times that of the Sun, placing it firmly in the ultramassive category of black holes that are more massive than 10 billion Suns. This places the black hole close to the theoretical upper limit for black hole masses, which is currently estimated to be around 50 billion Suns. This groundbreaking discovery offers valuable insights into the properties of black holes and their role in shaping the universe as we know it.
The discovery of the ultramassive black hole at the center of Abell 1201 BCG places it among the top 10 most massive black holes known to date. With a mass of 32.7 billion times that of the Sun, the diameter of its event horizon would span over 1,290 astronomical units, which is more than 30 times the distance between the Sun and Pluto. This incredible feat of nature is awe-inspiring and offers valuable insights into the mysteries of the universe.
While the detailed measurement of the black hole’s mass in Abell 1201 was made possible by the unique properties of its gravitational lens, Nightingale and his team believe that their approach holds promise for detecting and weighing other black holes in the distant universe. This could provide new opportunities for studying inactive black holes, which are currently difficult to observe in distant galaxies.
The team’s groundbreaking discovery could shed new light on the evolution of black holes over cosmic time and offer clues as to how they grow to such enormous sizes. The potential implications of this research are vast and could lead to new breakthroughs in our understanding of the universe.
The findings of this study have been published in the Monthly Notices of the Royal Astronomical Society and represent a major step forward in our knowledge of these enigmatic cosmic entities.
