JWST's best 'black hole star' candidate points to a shortcut for early supermassive black holes
MoM-BH*-1 shows the deepest Balmer break yet measured, which its discoverers read as a 100,000-solar-mass black hole inside a dense gas cocoon 660 million years after the Big Bang.
The Scientist · Science desk
What happened
- Astronomers using JWST's Miracle or Mirage (MoM) survey found the most promising candidate yet for a "black hole star", named MoM-BH*-1.
- The reddish light from MoM-BH*-1 was emitted about 660 million years after the Big Bang, when the universe was approximately one-twentieth its current age.
- Little red dots are hundreds of distant crimson lights spotted by JWST that shine much brighter than stars but are too dim to be fully formed galaxies, making them one of the biggest puzzles in modern astronomy.
- When JWST began observing the distant universe in summer 2022, astronomers found many little red dots; they are highly luminous as an active black hole would be, but their spectra are odd, looking more like stars, with no X-ray emission.
- If confirmed, the findings could help unravel the mysterious origin of little red dots.
Why it matters
Astronomers using JWST's MoM survey have reported the strongest candidate yet for a "black hole star": a compact red source, catalogued MoM-BH*-1, whose light was emitted about 660 million years after the Big Bang, when the universe was roughly one-twentieth its present age [1][2]. If the interpretation holds, it converts the "little red dot" problem from a question about impossibly compact galaxies into a question about how quickly black holes got heavy [5][6][14].
The little red dots are hundreds of faint crimson sources JWST began turning up in 2022 [3][4]. They are far brighter than stars but too dim to read as fully formed galaxies, and their spectra are the awkward part: luminous like an active black hole, yet shaped more like a star, with no X-ray emission [3][4]. Part of the difficulty has been separation. In most cases the dot's light is mixed with light from an unresolved host galaxy, according to the MoM team [7].
MoM-BH*-1 is unusually clean in that respect. The object outshines its host galaxy by a wide margin and is about 100 billion times brighter than a typical star, the researchers reported on 12 August in Nature [8][2][9]. It is also redder than most little red dots [10]. The obvious explanation for redness is dust, as MIT's Robert Simcoe noted: dust absorbs shorter blue wavelengths and leaves the rest [11]. But the spectrum shows a Balmer break, an abrupt absence of light below the wavelength of the hydrogen Balmer series, which indicates light passing through an extremely dense shell of gas rather than a dusty screen [12]. First author Rohan Naidu of the University of Hawaii and MIT says the break here is three to four times stronger than any previously seen, deep enough in his account to rule out ordinary stars as the source [13][15][16].
The object is also badly short of heavy metals, implying gas that is close to pure hydrogen and helium [22]. Simulations that try to reproduce both the break and the luminosity converge, the team says, on a black hole of about 100,000 solar masses wrapped in a dense cocoon [17]. That mass is only just inside supermassive territory [18]. The proposed mechanism is that accretion energy from the black hole is absorbed by the surrounding gas and re-radiated, doing the job nuclear fusion does in an ordinary star [19][6].
This is not the first such candidate. Last year, an overlapping group of authors described an object called the Cliff with similar features; MoM-BH*-1 sits farther away and therefore earlier, which is why the team treats it as the more informative case [20][21].
The formation route is unsettled. Options on the table include direct gravitational collapse of a gas cloud and the merger of a cluster of massive stars [24]. Naidu favours a supermassive star forming roughly 150 million years after the Big Bang, thousands of times the Sun's mass, which sheds a gas shell in an outburst and then collapses [25][26]. His local analogue is Eta Carinae, a roughly 100-solar-mass star whose 1840s outburst briefly made it the second brightest star in the sky and left the Homunculus Nebula [23]. He describes this as the hypothesis now needing to be proved or disproved [27].
What to watch: whether other little red dots yield Balmer breaks of comparable depth once host-galaxy light is subtracted, and whether the claim that every supermassive black hole descends from a first-generation giant star survives contact with a larger sample [7][28].
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence66
- Adoption30
- Hype gap+18
- Incentives55
- Confidence63
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Astronomers using JWST's Miracle or Mirage (MoM) survey found the most promising candidate yet for a "black hole star", named MoM-BH*-1.
- [2]
The reddish light from MoM-BH*-1 was emitted about 660 million years after the Big Bang, when the universe was approximately one-twentieth its current age.
- [3]
Little red dots are hundreds of distant crimson lights spotted by JWST that shine much brighter than stars but are too dim to be fully formed galaxies, making them one of the biggest puzzles in modern astronomy.
- [4]
When JWST began observing the distant universe in summer 2022, astronomers found many little red dots; they are highly luminous as an active black hole would be, but their spectra are odd, looking more like stars, with no X-ray emission.
- [5]
If confirmed, the findings could help unravel the mysterious origin of little red dots.
- [6]
An international team concludes that newborn and rapidly growing supermassive black holes could be powering the little red dots that litter the early universe.
- [7]
Until now there had been only circumstantial evidence for the black-hole star hypothesis, partly because in most cases the light from little red dots mingles with light from the unresolved host galaxy, clouding observations.
- [8]
MoM has found a black-hole star shining 100 billion times brighter than any known star and drastically outshining its host galaxy.
- [9]
The object is roughly 100 billion times brighter than a typical star, researchers reported in a study published Aug. 12 in the journal Nature.
- [10]
The first clue that MoM-BH*-1 was unusual was its striking ruby hue; it is redder than many other little red dots.
- [11]
Study co-author Robert Simcoe, director of MIT's Kavli Institute for Astrophysics and Space Research, said that when something very red is seen in the universe it is often assumed to be surrounded by dust, and that dust blocks shorter blue wavelengths, making remaining light appear redder.
- [12]
The spectrum is missing some wavelengths, a feature known as a Balmer break; below the wavelength corresponding to the Balmer series of hydrogen there is no light at all, which suggests the light is shining through an extremely dense shell of gas rather than dust.
- [13]
Naidu said: "In MoM-BH*-1 the Balmer break is three to four times stronger than any we've seen ever before... This feature alone tells us there is something truly singular afoot, and that this is a new kind of astrophysical object."
- [14]
Naidu, team leader, said: "A little red dot is an extraordinary object. Somewhere within it lies a black-hole star, surrounded by a good old fashioned galaxy."
- [15]
Study first author Rohan Naidu is an astronomer at the University of Hawaii and a former NASA Hubble fellow at MIT.
- [16]
Naidu said the Balmer break observed in this object is the deepest break ever observed in any object, ruling out ordinary stars as the source.
- [17]
Simulations modelling the Balmer break and the object's luminosity strongly suggest a 100,000 solar mass black hole at the centre of MoM-BH*-1, surrounded by an extremely dense cocoon of gas.
- [18]
The team estimates the black hole within MoM-BH*-1 weighs up to 100,000 solar masses, which is just large enough to qualify as supermassive.
- [19]
In the black-hole star picture, the black hole accretes gas from the interior of a dense cocoon and radiates energy that the cocoon absorbs, making it glow, replacing the role of nuclear fusion at the heart of a typical star.
- [20]
Last year a study including many of the same authors identified a black hole star candidate dubbed "the Cliff", which displayed many characteristics similar to MoM-BH*-1.
- [21]
MoM-BH*-1 is farther away and therefore older than the Cliff, making it more important for understanding how these objects form; the team calls it their best evidence for the object class.
- [22]
The object is severely lacking in heavy metals, suggesting the dense gas is composed almost purely of hydrogen and helium.
- [23]
Eta Carinae, a 100-solar-mass star, had an outburst in the 1840s that made it the second brightest star in the sky for several days and left a cocoon of gas called the Homunculus Nebula; massive Milky Way stars top out at a few hundred solar masses.
- [24]
Possibilities raised for how the black hole formed range from the direct gravitational collapse of a gas cloud to the merger of a cluster of massive stars.
- [25]
Naidu favours an explanation involving a supermassive star that could have formed about 150 million years after the Big Bang, when the universe was dense with hydrogen and helium; many popular models say those conditions spawned stars thousands of times the mass of the Sun.
- [26]
Naidu suggests a much larger supermassive star could have had an outburst leaving a gas cocoon and then collapsed to a black hole, creating a black hole star.
- [27]
Naidu said that in the past few months he has seen so much evidence for the supermassive-star route that it is now the main hypothesis that needs to be proved or disproved, because the similarities to supermassive stars are uncanny.
- [28]
Physics World reports it is possible that every supermassive black hole in the universe could be a relic of the very first giant stars created just after the Big Bang, with such objects steadily eroding their gaseous cocoon from the inside out.
Sources
2 independent publishers whose own reporting we read for this story.
Topics and entities
Topics
- JWST high-redshift spectroscopy
- Black hole stars
- Early supermassive black hole formation
Entities
- Miracle or Mirage (MoM) survey
- Chandra X-ray Observatory
- Institute of Science and Technology Austria
- MIT Kavli Institute for Astrophysics and Space Research
- Nature
- James Webb Space Telescope