A team of astronomers has made a groundbreaking discovery of a monster black hole in the early universe, which is consuming matter at rates exceeding the theoretical limits. This finding intensifies the ongoing mystery surrounding the rapid growth of certain black holes that were born shortly after the Big Bang. Utilizing NASA's Chandra X-ray Observatory, a powerful X-ray telescope, researchers focused on an ancient black hole named RACS J0320-35, which formed just 920 million years post-Big Bang.
During this early epoch of cosmic history, when the universe was merely one-fifteenth its current age, RACS J0320-35 was already an enormous entity, boasting a mass approximately 1 billion times that of the sun. This black hole is not just massive; it is growing at an astonishingly rapid pace. Analysis of the X-ray, infrared, and optical radiation emitted by the black hole indicates that it is expanding at 2.4 times the Eddington limit. The Eddington limit represents the theoretical ceiling for black hole growth, determined by the balance between their outward radiation pressure and gravitational pull.
Lead study author Luca Ighina from the Harvard and Smithsonian Center for Astrophysics expressed surprise at the black hole's unprecedented growth rate, stating, "It was a bit shocking to see this black hole growing by leaps and bounds." While RACS J0320-35 is not the first instance of a super-Eddington black hole found in the early universe, further investigation could provide crucial insights into why some ancient black holes appear to challenge our existing cosmological models. This groundbreaking research was published on September 8 in The Astrophysical Journal Letters.
Black holes are cosmic objects formed from the collapse of massive stars, creating gravitational sinkholes in space that can consume vast amounts of matter. They grow by merging with other black holes and by absorbing matter that crosses their event horizon—the boundary beyond which nothing can escape, not even light. As these colossal black holes attract matter at nearly the speed of light, they can create dazzling rings of light or expel energy in massive jets that extend across the cosmos. The most luminous of these entities are known as quasars, which can outshine entire galaxies with their radiant energy.
RACS J0320-35, initially discovered in a radio telescope survey, was later observed by Chandra in 2023. The bright emissions across the electromagnetic spectrum from this black hole make it an exemplary target for studying black hole growth. Researchers analyzed the intensity of X-ray light emitted from the black hole at various wavelengths and subsequently compared this data to infrared and optical observations to estimate its mass and growth rate.
The study revealed that RACS J0320-35 is likely consuming between 300 to 3,000 solar masses of matter each year, surpassing the Eddington limit for a black hole of its size. The question of how this black hole can exceed this limit without becoming unstable remains unanswered.
With a clearer understanding of the black hole’s growth rate and age, researchers hypothesized about its formation. They proposed that, due to its rapid growth, it may have originated similarly to many typical black holes in the local universe—formed from the collapse of a large star with a mass less than 100 solar masses. This finding, alongside other potential super-Eddington black holes detected by the James Webb Space Telescope in the early universe, suggests that fast-growing black holes could be more prevalent in the ancient cosmos than current models indicate.
Rapidly growing black holes like RACS J0320-35 may also be more likely to emit enormous energy jets, as observed in this case. Continued research into RACS J0320-35 and similar black holes will help scientists uncover the secrets behind the universe's earliest black holes, particularly regarding their origins and the mechanisms that enabled their rapid growth.
