A study in Nature finds that black holes in the early Universe go through short periods of ultra-fast growth, followed by long periods of dormancy. (Credit: Jiarong Gu)
In a nutshell
- Astronomers have discovered a massive black hole from the early universe that’s barely feeding — suggesting these cosmic giants may spend most of their lives in a dormant, low-activity state.
- The black hole outweighs its host galaxy’s stars by a factor of about 1,000, a ratio far higher than what we see in galaxies today, challenging our understanding of how black holes and galaxies grow together.
- This surprising find hints that the universe could be filled with hidden, under-the-radar black holes that escaped detection because they aren’t shining brightly, opening a new window into the unseen lives of early black holes.
CAMBRIDGE, England — The universe’s first black holes should be ravenous beasts, growing as quickly as possible. At least that’s what most astronomers thought. But astronomers using the James Webb Space Telescope have recently discovered an enormous black hole in the infant universe that’s essentially snoozing, consuming matter at a leisurely pace while mysteriously outweighing its host galaxy by enormous proportions. The discovery has astronomers questioning everything they thought they knew about these cosmic monsters.
This finding, published in Nature, challenges how we understand the way these cosmic behemoths form and grow. It suggests that black holes in the early universe might typically exist in a dormant state rather than in the actively feeding phase astronomers usually detect.
The Cosmic Oddball
The research team from the University of Cambridge spotted this unusual object in a galaxy called JADES GN-1001830. We’re seeing this galaxy as it existed just 760 million years after the Big Bang when the first galaxies were just beginning to light up the universe.
The key difference between this discovery and previous ones is that earlier black holes found by the Webb telescope were actively growing, consuming material at high rates and shining brightly, making them relatively easy to spot.
Finding a massive black hole that’s not actively feeding, essentially catching it during its downtime, reveals that these objects may spend most of their lives in this quiet state. The fact that astronomers found such an object despite numerous factors working against its detection suggests that dormant black holes were quite common in the early universe.
The team spotted this cosmic sleeper by identifying a specific emission pattern in the galaxy’s light. This pattern reveals gas moving at high speeds near the black hole at about 5,700 kilometers per second (or 12.8 million miles per hour). By measuring this motion, they calculated the black hole’s impressive mass.
Because the black hole wasn’t outshining its host galaxy, the researchers could study the galaxy itself in unusual detail. They found it’s relatively small, with a half-light radius of about 447 light-years (our Milky Way, for comparison, has a half-light radius roughly 50 times larger), and shaped like a flat disk. The galaxy is forming new stars at a rate of about 1.4 times the mass of our Sun each year, actually below average for galaxies of similar size at that time in cosmic history.
The Growth Mystery
The relationship between the black hole and its host galaxy is not the norm. While the black hole is dramatically oversized compared to the galaxy’s star mass, it’s closer to expected values when compared with the galaxy’s total mass and internal motion. This hints that the host galaxy’s total matter is already in place, but star formation is lagging behind, possibly because energy or outflows from the black hole have suppressed it.
Some researchers think the first supermassive black holes grew from heavy “seeds,” gas clouds that collapsed directly into black holes thousands of times more massive than our Sun. Others propose they started from lighter seeds (remnants of the first stars) but experienced episodes of extremely rapid growth, exceeding their theoretical feeding limits during short, intense bursts.
The sleepy black hole in JADES GN-1001830 fits better with the second scenario. Computer simulations show that brief periods of super-fast growth could produce black holes that rapidly become very massive, followed by long quiet periods when they’ve essentially run out of easily accessible fuel or pushed it away through their intense activity.
Hidden Giants Throughout the Universe
To figure out how common this could be, the researchers ran simulations to assess their ability to detect black holes of various masses and feeding rates. They discovered that black holes consuming material more vigorously are naturally easier to spot. Finding this dormant black hole hints it represents just the tip of the iceberg. It happened to be massive enough to detect despite its low activity level, but countless others likely lurk beyond our current detection capabilities.
Finding such an object among the 35 galaxies they studied in this region of space is a huge win for astronomers, especially considering that their search methods actually work against finding distant galaxies with low star formation rates, which is precisely the type of galaxy where this dormant black hole was found.
This sleeping giant forces us to question whether black holes might live most of their lives in quiet dormancy rather than constant feeding frenzies. The universe could be filled with these snoozing titans hidden not because they’re rare, but because we’ve been looking for the wrong signatures. By catching this one during its cosmic nap, astronomers have opened a window into understanding the true lifecycle of the universe’s most extreme objects.
Paper Summary
Methodology
The research used data from the James Webb Space Telescope’s survey of distant galaxies. The team analyzed light from the galaxy using special instruments that break light into its component wavelengths. They identified a pattern in the light that showed gas moving rapidly near the black hole. Using multiple camera filters, they separated light from the black hole region from that of the surrounding galaxy. The researchers then used computer modeling to determine the galaxy’s properties.
Results
The analysis revealed a black hole roughly 400 million times the mass of our Sun, consuming material at only 2.4% of its maximum possible rate. The host galaxy contains stars with a combined mass of about 830 million Suns and is forming new stars more slowly than similar galaxies from that era. The black hole’s mass is about 40% of its galaxy’s star mass – roughly 1,000 times higher than the ratio we see in nearby galaxies today. However, when compared with the galaxy’s total mass including gas, the black hole’s size is closer to what we’d expect from patterns seen in the present-day universe.
Limitations
The study faces several challenges. The measurements have some uncertainty because the galaxy is so distant, and the light signals are relatively faint. The researchers had to make assumptions about dust blocking some of the light based on indirect evidence. The estimate of the galaxy’s total mass might be on the low side because they couldn’t capture the full rotation of the galaxy in their observations. Also, since they’ve only found one such object, it’s difficult to draw broad conclusions about how common these dormant black holes might be in the early universe.
Discussion and Takeaways
This discovery challenges previous explanations for why distant black holes appear oversized relative to their host galaxies. Models that allow for brief periods of extremely rapid growth better match what they observed than scenarios requiring steady, more modest growth rates. This suggests black holes might grow through short, intense feeding frenzies followed by extended periods of dormancy. The fact that this black hole’s mass makes more sense when compared to the galaxy’s total mass and internal motion, rather than just its star mass, suggests the galaxy’s total matter is already in place, but something – possibly past black hole activity – has slowed down star formation.
Funding and Disclosures
This research received support from numerous sources, including the Science and Technology Facilities Council, the European Research Council, the Spanish Ministry of Science and Innovation, and various other grants. Several researchers also received support from individual institutions including St Catharine’s College, the PRIN 2022 MUR project, and INAF Theory Grants.
Publication Information
The study, “A dormant overmassive black hole in the early Universe,” appeared in Nature, Volume 636, published December 19/26, 2024. The lead author, Ignas Juodžbalis, is from the Kavli Institute for Cosmology and Cavendish Laboratory at Cambridge University, with co-authors from institutions throughout Europe and the United States. The paper is available online through Nature‘s website.
