When Charlotte Mason contemplates cosmic mysteries, she finds herself doodling. “I’m quite a visual person,” she remarks. “I usually sketch a lot to try and understand what’s happening.” Mason, an astrophysicist at the Cosmic Dawn Center in Copenhagen, has recently been filling pages with sketches of “little red dots,” perplexing objects that have been discovered in abundance through images from the James Webb Space Telescope (JWST). These elusive red dots were previously unseen until the telescope became operational in 2022. However, they are believed to have started appearing in significant numbers approximately 650 million years after the Big Bang.
These dots represent one of the many captivating enigmas that have emerged from JWST’s observations of the early universe. Additional mysteries include black holes that appear astonishingly large for their age and ancient galaxies that challenge our previous understanding of the first billion years following the Big Bang. Initially, scientists were astounded; the universe unveiled by the JWST simply did not align with existing astrophysical knowledge. Now, a surge of new theories presents intriguing solutions, yet determining which of these accurately reflects reality remains an unresolved issue.
New Insights into Cosmic Objects
Recent theories suggest that these little red dots might be black holes shrouded in a dense gas cloud, potentially representing a completely new type of object called a “black hole star,” where the thick gas envelope emits light akin to a stellar atmosphere. “This would be my black hole,” Mason said, sketching a small circle and filling it in. “Perhaps I’ll add a disk, because we believe that some of the emission comes from there.” She drew a line through the centre of the circle. “So, the rather simplistic image is just this dense gas cloud around the black hole.” She then annotated the sketch with a larger circle surrounding the object.
However, Mason suspects that these cosmic puzzles might conceal something deeper. She and her colleagues recently examined the light spectrum emitted by one of the little red dots. If the image of the dense cloud were accurate, part of the light should have altered as it passed through the gas, but that’s not what they observed. “So what do I do now? I start over. But now, if I cluster the gas into clumps,” Mason remarked, drawing a new diagram with gaps in the clouds surrounding the black hole, “I should be able to get [a signal] that looks closer.”
Across the globe, researchers like Mason are eagerly piecing together the JWST’s images of the early cosmos to create a clearer picture of our universe’s origins. And much like the photons that travel billions of light-years to reach us, new fragments are continuously falling into place.
The Complexity of Black Holes
The narrative surrounding black holes has become more intricate thanks to the JWST, which continues to detect ancient black holes that are too massive to be explained by established theories. Shortly after the Big Bang, the universe was largely smooth and featureless. Yet, merely a few hundred million years later, “we already see black holes with masses of billions of suns,” asserts Jenny Greene, an astrophysicist at Princeton University. “For them to reach that size so quickly, one has to juggle a lot of factors.”
Scientists consider two key factors influencing a black hole’s size: the mass of the “seed” black hole at its inception and the rate at which these seeds grew thereafter. However, explaining how black holes formed at such sizes or grew rapidly enough to reach a mass a billion times that of the Sun in the universe’s infancy remains a challenge. In the current universe, black holes form when the core of a massive star exhausts its fuel and collapses. Given that the earliest stars were quite massive, they could have left behind black hole “seeds” of around 100 solar masses, Greene explained.
“We know that happens, but it’s very, very difficult for them to reach a billion so quickly,” she added. “They really have to be force-fed.” Historically, scientists believed there was a strict limit to how fast black holes could grow. As matter spirals into a black hole, it heats up as it spins around, much like water draining down a sink. The radiation produced by this “accretion disk” pushes against the incoming material, preventing the black hole from consuming more. This intake limit, known as the Eddington limit, should render it impossible for black holes to grow several tens of millions of times more in the available time.
Exploring Theories of Formation
Recent computer simulations suggest that black holes might possess a kind of “back door.” If the accretion disk expands in just the right way, incoming gas can overcome the radiation pressure, leading to accretion that channels gas at extraordinary velocities. Nevertheless, astronomers are still unsure whether there was enough gas surrounding them to account for the largest black holes. Some researchers believe that ancient and dense star clusters could have rapidly merged numerous black hole seeds.
Alternatively, supermassive black holes may not have formed from stars at all. In this scenario, colossal gas clouds could have sunk directly into a black hole. This “direct collapse” mechanism could yield a seed with a mass around 10,000 times that of the Sun. “The problem with the direct collapse hypothesis is that it requires really perfect conditions,” Greene noted. For direct collapse to occur, a gigantic cloud must compress into a black hole all at once without first fragmenting into smaller clouds that would form stars. This necessitates specific chemical compositions of the gas, and the cloud must rotate slowly.
“When you simulate this on a computer, you can create these black holes through direct collapse, but you can’t generate enough of them to explain all the black holes we observe,” Greene added. There is some evidence to support each of these theories. In 2024, the JWST observed a black hole from about 1.5 billion years after the Big Bang consuming matter at a rate roughly 40 times the Eddington limit. If black holes from earlier epochs also fed in this manner, perhaps the largest among them began as relatively small seeds.
Recently, researchers closely examined a little red dot dating back approximately 750 million years after the Big Bang, which is experiencing gravitational lensing due to a foreground galaxy cluster. They concluded that the object is a “naked” supermassive black hole, estimated to have a mass of 50 million times that of the Sun, with no discernible stars surrounding it. If that mass estimate is accurate, the implication is that the black hole may have formed from a large seed, possibly through direct collapse, before any galaxies existed.
“It’s clear that there are differences in how black holes grow that we don’t yet fully understand,” Greene admitted. “So, for me, the most exciting thing right now is trying to understand, from a physical perspective, what the difference is.”
Understanding Early Galaxy Formation
Much like the early black holes that appear too large, many of the first galaxies detected by the JWST seem excessively bright. To uncover the reasons behind this, researchers are rethinking their ideas on galaxy formation. About 200 million years after the Big Bang, the early universe was small, dense, and hot compared to today. As it expanded and cooled, dark matter clumped together into large clusters that scientists refer to as halos. The gravity of these dark halos attracted gaseous hydrogen and helium into vast filaments that clustered in the cores of the dark orbs surrounding them. Once enough gas accumulated, extreme pressures triggered nuclear fusion processes, igniting the first stars, which grouped together to form the first galaxies.
Astronomers often describe the chronology of these events in terms of redshift—how much the light from the earliest objects has stretched due to cosmic expansion. “Not much happens until you reach a redshift of about 15 [270 million years after the Big Bang], and then a lot of gas starts flowing along these filaments,” explained Rachel Somerville, a senior research scientist specialising in galaxy formation at the Flatiron Institute in New York. At a conference held in April 2026 in Helsingør, Denmark, attended by over 100 researchers from around the world to discuss the mysteries of the universe’s infancy, she presented new computer simulations. Colourful visualisations of dark matter, gas, and stellar light danced on the projector screen.
“Around a redshift of 11 [420 million years], the star formation rate really starts to pick up,” she continued. “At a redshift of 9 [550 million years], a lovely galaxy forms.” The galaxy displayed on the screen illustrated a primitive population, yet the oldest galaxy discovered thus far by the JWST existed just 280 million years after the Big Bang. The telescope’s astonishing discovery of primitive and bright galaxies initially led some scientists to suggest that our fundamental understanding of cosmology (the laws governing energy and matter behaviour in the early universe) might be flawed. However, after several years of studying these primitive objects, theorists now possess multiple models to explain their brightness and abundance.
“We’ve almost gone from having too many primitive galaxies to having too many theories to explain them,” Somerville stated to the audience.
Perhaps the earliest galaxies converted gas into stars more efficiently than previously thought. Alternatively, they may have experienced periodic bursts of star formation driven by turbulent conditions. Or it’s possible that early star-forming regions preferentially created massive and exceptionally bright stars. Many astrophysic