A team of MIT astronomers has uncovered tantalizing clues about the origins of some of the universe’s most enigmatic objects: black holes.
They used the James Webb Space Telescope (JWST) to collect data on distant quasars, which are extraordinarily luminous objects powered by black holes.
Webb peered back more than 13 billion years to a time when the universe was still in its infancy. The observations provided crucial insights into the evolution of the earliest black holes and galaxies.
The powerful space observatory detected “elusive starlight” from around three ancient quasars.
Webb’s data indicated that the black holes fueling these quasars were significantly larger than their host galaxies compared to their current equivalents.
How black holes turned out to be so massive in the early universe is one of the greatest cosmic enigmas of today’s time.
Webb’s 120-hour observations reveal that some of the “earliest monster black holes grew from massive cosmic seeds.”
“After the universe came into existence, there were seed black holes that then consumed material and grew in a very short time. One of the big questions is to understand how those monster black holes could grow so big, so fast,” said Minghao Yue, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research.
The intriguing primordial seeds
Back then, the primordial seeds may have provided the starting point for the growth of black holes, which eventually evolved into “monster” black holes by devouring cosmic matter from their vicinity.
But what kind of seeds? Previous studies have suggested various scenarios that may have led to the formation of extremely massive black holes in the young universe.
One possibility is that supermassive black holes start from relatively small black holes formed in the deaths of massive stars, known as supernovae. Over time, they accumulate more and more matter to become supermassive.
Another possibility is that supermassive black holes result from the direct collapse of massive gas clouds in the early universe. This direct collapse scenario would form a much larger seed black hole to start with.
“Our results imply that in the early universe, supermassive black holes might have gained their mass before their host galaxies did, and the initial black hole seeds could have been more massive than today,” said Anna-Christina Eilers, assistant professor of physics at MIT.
Black holes’ mass higher than their host galaxies
Detecting light from distant quasars is challenging due to their extreme brightness, which might outshine their home galaxy. Furthermore, it isn’t easy to distinguish the light between the quasar’s core black hole and that of the host galaxy’s stars.
However, Webb’s higher sensitivity and resolution allowed the MIT team to make these observations of quasars, which are roughly 13 billion years old. Quasars offer a window to study the enigmatic black holes, which do not reflect light, making them undetectable to telescopes.
“The quasar outshines its host galaxy by orders of magnitude. And previous images were not sharp enough to distinguish what the host galaxy with all its stars looks like,” Yue mentioned.
The data indicated that the mass ratio between the core black hole and the host galaxy was around 1:10. Today’s mass balance is projected to be 1:1,000, suggesting that black holes are less massive than host galaxies.
“This tells us something about what grows first: Is it the black hole that grows first, and then the galaxy catches up? Or is the galaxy and its stars that first grow, and they dominate and regulate the black hole’s growth?” Eilers concluded in the press release.
Several missing pieces remain in the puzzle to decode how the black holes turned out to be so massive in the early cosmos.
The study results have been published in the Astrophysical Journal.
