Illustration of cosmic winds emanating from a quasar’s black hole accretion disk.
Credit: NASA/CXC/M. Weiss, Catherine Grier and the SDSS collaboration.
Albert Einstein published his general theory of relativity in 1915, which described gravity as the effect of mass distorting the fabric of spacetime. A century later, advances in observational astronomy are increasingly capable of studying the most extreme distortions predicted by his theory – black holes. This blog summarizes some of the latest research findings about black holes.
Supermassive Black Holes
Supermassive black holes millions to billions of times the mass of the Sun are believed to reside at the centers of most large galaxies. Recent studies have shed light on the growth of these colossal objects and their role in the evolving structure of the universe.
In operation for only two years, the James Webb Space Telescope (JWST) has detected the most distant pair (to date) of merging black holes located more than 13 billion light-years away, or just 740 million years after the Big Bang. The merging black holes have estimated masses of about 50 million times that of the Sun. Their enormous size at such an early stage in the universe’s history indicates that black holes existed and grew rapidly during the universe’s infancy.
Researchers at Johns Hopkins University have reported that black holes were crucial in accelerating star formation in the early universe. Powerful cosmic winds and magnetic fields surrounding black holes compressed nearby gas clouds, triggering the formation of new stars at an unprecedented rate. The researchers believe that the young universe underwent two distinct phases. During the first phase, high-speed outflows from black holes accelerated star formation. In the second phase, these outflows slowed, and gas clouds collapsed due to supermassive black hole magnetic storms, leading to even higher rates of star birth.
Another study suggests that the supermassive black hole at the heart of our Milky Way galaxy had a late growth spurt, indicating that black hole growth can occur in bursts rather than steadily over time.
Black Hole Cosmic Winds
A team of researchers at the University of Wisconsin–Madison studied accelerating gas from a quasar in the constellation Boötes. (A quasar is a type of active galactic nucleus powered by a supermassive black hole in a young galaxy.) As the material in the disk falls into the black hole, friction makes the disk extremely hot and bright. The wide range of temperatures from the interior to the outer parts of the disk results in emissions covering almost all of the electromagnetic spectrum. The intense energy pushes clouds of gas outward among neighboring stars at more than 10,000 miles per second, as illustrated above. These cosmic winds are another way black holes likely affect their surrounding galaxies.
Black Hole Reawakening
In 2019, galaxy SDSS1335+0728 suddenly began shining brighter than ever before. To understand why, astronomers used data from multiple space and ground-based observatories to track how the galaxy’s brightness varied before and after it lit up. The data show that SDSS1335+0728 is now radiating much more light at ultraviolet, visible, and infrared wavelengths, and since February 2024, it has also been emitting X-rays. These findings indicate the sudden reawakening of the galaxy’s massive black hole.
Other phenomena can make galaxies suddenly light up, like supernova explosions or tidal disruption events when a star gets too close to a black hole. But in these cases, the increased brightness typically lasts weeks or, at most, a few months. Yet, SDSS1335+0728 is growing brighter, nearly five years after it was first seen to ‘switch on’.
Possible Role of Black Holes in the Expanding Universe
Another recent study suggests a potential link between supermassive black holes and the expanding universe.
A team of researchers led by the University of Hawaii studied supermassive black holes in dormant elliptical galaxies. These massive black holes formed when the universe was only a fraction of its current age and grew faster than can be explained through local processes, such as disk accretion or mergers. The researchers theorize that black holes gain mass coupled to the expansion of spacetime itself. This scaling relationship suggests a deep connection between the cosmos’ large-scale structure and the black holes’ local properties.
While the cosmological coupling theory raises intriguing possibilities to explain dark energy (the hypothesized cause of the universe’s accelerating expansion), further theoretical exploration and observational verification are needed. Other research groups have proposed different mechanisms for the rapid growth of black holes. Future studies should be able to validate or invalidate the competing theories.
Summary
Since Einstein’s field equations of general relativity predicted the existence of black holes, our understanding of them has come a long way. With today’s astronomical instruments, their role in the structure and evolution of the cosmos is becoming clear. Still, there is more we don’t know that we do know about black holes. The study of black holes is one of the most active areas of astrophysical research, so we should know more about them in the near future.
