A team of MIT astronomers has made groundbreaking discoveries about the origins of some of the universe’s most mysterious objects: black holes. Using the James Webb Space Telescope (JWST), they collected data on distant quasars, incredibly luminous objects powered by black holes, peering 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. Webb detected “elusive starlight” from around three ancient quasars, indicating that the black holes fueling these quasars were significantly larger than their host galaxies compared to their modern-day counterparts.
Unraveling the Mystery of Early Supermassive Black Holes
One of the greatest cosmic enigmas of our time is understanding how black holes became so massive in the early universe. Webb’s 120-hour observations reveal that some of the “earliest monster black holes grew from massive cosmic seeds.”
Minghao Yue, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research, explained, “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.”
The Role of Primordial 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, and accumulate more matter over time.
Another possibility is that supermassive black holes result from the direct collapse of massive gas clouds in the early universe, forming much larger seed black holes from the start.
“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.
Overcoming Observational Challenges
Detecting light from distant quasars is challenging due to their extreme brightness, which might outshine their home galaxy, and the difficulty in distinguishing 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 that are roughly 13 billion years old. The data indicated that the mass ratio between the core black hole and the host galaxy was around 1:10, compared to today’s projected mass balance of 1:1,000, suggesting that black holes are less massive than host galaxies in the modern universe.
Implications for Galaxy Formation and Evolution
The findings raise questions about the interplay between black holes and their host galaxies in the early universe. “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.
While several missing pieces remain in the puzzle to decode how black holes turned out to be so massive in the early cosmos, the study’s results, published in the Astrophysical Journal, provide a significant step forward in our understanding of the early universe and the evolution of supermassive black holes.
