The James Webb Space Telescope is still turning up an early universe that does not fit neatly with long-standing models. Observations now include billion-solar-mass black holes appearing within the first billion years after the Big Bang, ancient galaxies that look brighter than simulations expected, and large numbers of mysterious objects known as “little red dots,” a population that had not been seen before JWST launched in 2022.
According to Quanta Magazine, which spoke with several astrophysicists, the new data is pushing researchers toward competing explanations rather than a single clean fix. The problem is not limited to one puzzle. Black hole growth, galaxy formation, and the nature of little red dots may be connected, while some observations appear to favor different theories at the same time.
Black holes grew to enormous sizes unusually early
Princeton astrophysicist Jenny Greene said the post-Big Bang universe should have started out relatively smooth, yet only a few hundred million years later astronomers are already seeing billion-solar-mass black holes in the process of growing. In the standard picture, the first generation of stars would leave behind seeds of only about 100 solar masses. Reaching such extreme masses so quickly would require very aggressive feeding.
Black hole growth has traditionally been discussed in terms of the Eddington limit, but newer simulations suggest that under certain conditions an accretion disk can expand in a way that lets gas overpower radiation pressure, allowing “super-Eddington accretion.” In 2024, JWST observed a black hole from about 1.5 billion years after the Big Bang consuming matter at roughly 40 times the Eddington limit. That result supports a scenario where small seeds bulk up at extraordinary rates.
Another line of thinking argues that some of the largest black holes did not begin as stellar remnants at all. Instead, massive gas clouds may have collapsed directly into seeds of roughly 10,000 solar masses. Greene said direct-collapse black holes can be produced in simulations, but not in numbers large enough to explain the full population.
A recent study added fresh support for the large-seed idea. One little red dot from about 750 million years after the Big Bang, magnified by gravitational lensing, was identified as a “naked” supermassive black hole with an estimated mass of 50 million suns. Researchers could not identify surrounding stars, raising the possibility that it formed before any recognizable galaxy around it.
Early galaxies appeared too soon and looked too bright
The galaxy side of the story is just as difficult. Flatiron Institute scientist Rachel Somerville presented simulation results at a meeting in Helsingør, Denmark, in April. In those models, not much had happened by redshift 15, or about 270 million years after the Big Bang. By redshift 9, around 550 million years, the simulations produced a more developed galaxy.
JWST, however, has found the oldest galaxies at only about 280 million years after the Big Bang. They also look unusually bright. Proposed explanations now range from more efficient gas-to-star conversion in early galaxies, to bursty star formation, to conditions that favored especially luminous stars. Somerville said the field has shifted from having too many galaxies it could not explain to having too many theories trying to explain them.
Data from the MIRI instrument suggests the early galaxy population was highly diverse. Hakim Atek of Sorbonne University told Quanta Magazine that some galaxies appear to have cleared out their gas and dust, leaving exposed stars, while others remain packed with gas. That split points to the possibility that star formation in the early universe happened in repeated bursts rather than as a smooth process. Another group of galaxies with unusually high nitrogen content hints at the presence of many very massive stars in that era.
Little red dots may represent a new kind of object
The little red dots may be the strangest part of all. Charlotte Mason, an astrophysicist at Copenhagen’s Cosmic Dawn Center, has been studying them closely. These objects begin appearing in large numbers around 650 million years after the Big Bang, and there had been no prior observations of them before JWST.
One recent idea is that little red dots are black holes wrapped in thick gas, a proposed new class sometimes described as “black hole stars.” In that picture, a dense gaseous shell shines in a way similar to a stellar atmosphere. But when Mason analyzed the spectrum of one little red dot, she did not find the signal that dense gas clouds should have produced. She told Quanta Magazine that the model may need to be rebuilt, for example by making the gas clumpy or introducing holes around the black hole, and then checking whether the result matches the data more closely.
Different observations are pulling theories in different directions
At the moment, the evidence does not point to one unified answer. The black hole growing at 40 times the Eddington limit backs the small-seed, rapid-accretion route. The “naked” black hole with a mass of 50 million suns looks more compatible with a large-seed, direct-collapse origin. On the galaxy side, the diversity seen by MIRI also suggests there is no single script for every early system.
Researchers are now leaning on better simulations and more detailed observations to sort out the contradictions. Somerville said numerical modeling has made major progress, while Atek noted that matching observed galaxies with the closest analogs in simulations could help reconstruct their star-formation histories. JWST has not settled the story of the early universe. It has widened the gap between observation and expectation, and made that gap much harder to ignore.