Astronomers Stunned by a New Type of Cosmic Object - critical summary review

For four years, almost every deep image taken by the James Webb Space Telescope — NASA's infrared observatory, the successor to Hubble — has come back with the same nuisance in it: tiny, intensely red points that fit no known category of celestial object. They were first spotted in 2022 and nicknamed little red dots. Last week, a paper in the journal Nature, published on 12 August, offered an answer for at least one of them, and the answer is a kind of object nobody had catalogued before: a black hole so wrapped in gas that it shines like a star.

The red dot that behaved like neither a star nor a black hole

The object is called MoM-BH*-1. It sits in the constellation Cetus, the Whale, billions of light years from Earth, and is seen as it was roughly 660 million years after the Big Bang — the leading theory for how the universe began. It is, according to the authors, the reddest object in Webb's entire image archive.

Nobody was looking for it. The research came out of a project called MoM, short for "Mirage or Miracle", which hunts for the earliest and brightest galaxies and repeatedly runs into objects that look like galaxies and turn out to be something else. The team, with researchers from the Massachusetts Institute of Technology and the University of Bologna in Italy, spent nearly four years on these dots.

What made this one impossible to file away is the mismatch between size and output. Measurements suggest a black hole about 100,000 times the mass of the Sun, wrapped in a shell large enough that the whole structure would span the Solar System. That much makes it sound like an enormous star. But it releases 100 billion times more energy than any known star can produce — an output in the range of black holes, not stars.

"We have found a new type of astrophysical object, a black hole star," said Rohan Naidu, the study's lead author, who did the work at MIT's Kavli Institute for Astrophysics and Space Research and is now at the University of Hawaii. It "shines with the energy typically associated with black holes, but at the same time bears signatures classically associated with stars," he added. In a separate statement: "You have something that looks a bit like a star, but is 100 billion times brighter. That means it cannot be powered by nuclear fusion, which is the energy source at the heart of every star we know."

How dust and an ordinary star were ruled out

The obvious explanation for anything that red is dust. Distant objects tend to look reddish because dust blocks blue light more easily, and dust was one of the main hypotheses on the table for the little red dots generally.

Two things got in the way. First, the shape of the light. Broken down by wavelength, the object's brightness does not fade gradually — in one band it collapses by more than twenty times. That abrupt drop has a name, the Balmer break, and it is a signature of stars a few million years old, such as Vega, one of the brightest stars in the night sky, 25 light years away in the constellation Lyra. Except that here the drop is far more violent. "The break observed in the object is the deepest ever seen in any object, which takes an 'ordinary' star off the table as its real source," Naidu said. The readings also turned up essentially nothing but hydrogen and helium.

Second, the energy. The team ran simulations and could not find any conventional way to produce that much output from a star. When a black hole was put into the models instead, the numbers matched. The picture that came out is a growing black hole feeding on matter at the centre, surrounded by an enormous quantity of extremely dense, turbulent gas. That gas acts as a shroud: the bluer light produced near the black hole cannot escape, while redder wavelengths get through. The red, in other words, would come from gas rather than dust — and nearly all the light we see would come from the black hole and its surroundings, with little contribution from the galaxy hosting it.

What this settles about the little red dots — and what it unsettles

If the interpretation holds, MoM-BH*-1 is not a one-off curiosity. It becomes a template for the scores of little red dots showing up in nearly every deep Webb image. The dots appear in the era astronomers call Cosmic Dawn, around 600 million years after the Big Bang, and vanish a few hundred million years later.

The consequence runs in an awkward direction. Masses inferred for these objects assumed you were looking at something whose light you could read straightforwardly. If you are instead looking at a black hole through a thick curtain of gas, those masses may have been overestimated — which would change the arithmetic on how the first giant black holes grew so fast.

Naidu goes further, and this is his reading rather than a measurement: he suspects black hole stars play a major role in the evolution of galaxies and may be the seeds of today's supermassive black holes, including the one at the centre of the Milky Way. "For decades we have anticipated something spectacular must be afoot in the very early universe. Black hole stars may be the 'something spectacular'," he said.

An older clue: the X-ray that did not arrive

The idea did not appear from nowhere. In April, NASA's Chandra X-ray Observatory detected X-rays from one of these little red dots for the first time, and the analysis pointed to a black hole wrapped in a large cloud of gas — though it could not identify which gas. Two hypotheses were left standing: gas thick enough to form a star-like shell, or some unusual kind of dust. Those observations also indicated the gas around the black hole was being consumed by it, and that this was what was suppressing the X-rays typical of a supermassive black hole. The Nature paper adds a second, better-characterised example on the gas side of that fork.

The bigger puzzle: how giant black holes get big so fast

The question underneath all of this is, in the words of Steven Finkelstein, an astronomer at the University of Texas at Austin, "one of the most important questions in astrophysics". Small black holes are understood: a dying star explodes, collapses, and leaves something a few times the Sun's mass. Supermassive black holes are millions or billions of solar masses, and Webb keeps finding far more of them in the early universe than anyone expected.

Days after the black hole star paper, a study in Astronomy & Astrophysics published on Wednesday the 13th described the first evidence of a young galaxy hosting three active supermassive black holes. The galaxy, J0148-4214, is more than 12.5 billion light years away, placing it about a billion years after the Big Bang. The smallest of the three has the mass of 600,000 Suns, the largest 80 million. Two are close enough that their gravity should be pulling them together; by the calculations of lead author Hannah Übler, of the Max Planck Institute for Extraterrestrial Physics, they will merge in roughly 700 million years. "The assumption was always that these black holes started growing in the early universe," Übler said. "Now we are seeing it in action."

Giovanni Mazzolari, a postdoctoral researcher at Max Planck and co-author, lists the competing explanations: some black holes may simply be born heavy, some may devour matter at extraordinary rates, and mergers like this one may be common enough to do the job.

What the authors say they still do not know

The researchers are explicit that the black hole star is an interpretation built to fit the observations, and that how such objects form remains an open question. Naidu's team frames the dense-gas envelope as the model that survived their simulations, not as a measured fact. Their stated next step is data Webb cannot supply on its own — including future radio telescopes, which could reveal properties the infrared spectrum does not carry.

What to do with this information

This is not a story to check daily. It is one to come back to when the next batch of results lands, and there are two specific things that will settle it.

The first is reclassification. If other little red dots in Webb's catalogue start being reinterpreted as black hole stars, the practical consequence is that mass estimates for early galaxies published over the past few years get revised downward — which affects not just those objects but the timeline for how quickly the first supermassive black holes assembled. Watch for papers that revisit existing dots rather than announce new ones.

The second is the wavelength. The whole model rests on dense gas, not dust, producing the red. Radio and X-ray observations are the tests the authors themselves point to, because they probe the environment around the black hole in ways infrared cannot. Chandra's April detection is the precedent for how that kind of confirmation arrives, and how partial it can be: it established a gas shroud without identifying the gas.

Two reference points make the next headlines readable. One, the objects at issue are confined to a narrow window in cosmic history — they show up around 600 million years after the Big Bang and disappear a few hundred million years later — so a claim about a nearby analogue is a different claim. Two, "black hole star" is a nickname for a proposed structure, not an established class; the Nature title describes a gas-enshrouded, gas-reddened black hole. Whether it becomes a genuine new category or an interpretation that does not survive more data is precisely what the next round of observations is for.