A tiny red dot, spotted nearly 11.8 billion light-years away, emits X-rays where astronomers would have expected silence. This exception, observed by the Chandra and Webb telescopes, could shed light on the nature of the ‘little red dots’, those very distant objects that have emerged in observations of the young Universe. It is not enough to settle the debate, but it offers a clue as to what might lie behind their red light.
A family revealed by Webb
Since the James Webb Space Telescope began its scientific observations, astronomers have been spotting small red objects at great distances. Their light travelled for around 12 billion years or more before reaching us. These sources have been nicknamed ‘little red dots’.
Their appearance does not tell us directly what they are. The colour seen in an image depends on the light received by the instrument and on how it is represented; it is not equivalent to a colour photograph as the human eye would see the object. To understand these sources, teams combine observations at different wavelengths and study their spectrum in particular—that is, the distribution of their light according to wavelength.
One explanation under discussion is that they are rapidly growing supermassive black holes buried in thick envelopes of gas. A black hole is not visible in itself: it is, among other things, the matter falling towards it and heating up that can produce detectable radiation. If a dense gas cloud surrounds this region, it can obscure some of the ultraviolet signals and X-rays that astronomers usually use to identify an active black hole.
This scenario, sometimes described as a ‘black hole star’, could explain why some red dots resemble stellar atmospheres while harbouring a compact, energetic object. But the absence of detected X-rays in many cases is not, on its own, proof of this interpretation: the radiation may be absorbed or too faint for the observations available.
The exception uncovered in Chandra’s archives
The object at the centre of the new study is officially named 3DHST-AEGIS-12014. It is about 11.8 billion light-years away and displays several features associated with little red dots: it is compact, red and very distant. Its distinctive feature is that it also emits X-rays, unlike most members of this family known to date.
This source was not revealed by a new mission. It had been in the data from a deep survey by the Chandra Observatory, which specialises in X-rays, for more than ten years. Webb observations then made it possible to locate and characterise the object more precisely. The combination of the two observatories is crucial: Webb helps examine the infrared light from sources in the young Universe, while Chandra detects high-energy radiation that can indicate matter heated near a black hole.
The discovery thus highlights a practical limitation of astronomical observation: an archive can contain a remarkable object without its significance being immediately apparent. A measurement takes on a different meaning when compared with new data, at another wavelength or in light of a scientific question that had not yet been formulated.
A gap in the veil, or another explanation
The researchers suggest that the object is a little red dot in transition. In this interpretation, the black hole would gradually consume the gas around it. Less dense regions in this cloud would then allow some of the X-rays produced near the black hole to escape. Eventually, the veil of gas could dissipate, revealing a growing supermassive black hole more like those observed in other galaxies.
Chandra’s data also show signs of variations in X-ray brightness. These are consistent with an irregular cloud: as regions of different densities pass in front of the source, the amount of radiation reaching us can change. This variability supports the idea of a partially obscured object, but does not by itself prove that the transition scenario is correct.
Another possibility remains open: it could be a more common type of growing black hole, hidden behind unusual dust. The researchers therefore do not present this object as the definitive solution to the mystery. It is an unusual case, potentially useful for linking two categories of objects, whose exact nature has yet to be established.
Two discoveries, two levels of evidence
Little red dots do not necessarily form a uniform population. In November 2025, the European Space Agency announced that the Webb telescope had identified signs of an accreting black hole in the galaxy CANUCS-LRD-z8.6, observed as it was about 570 million years after the Big Bang. The NIRSpec spectrograph measured features in the light indicating strongly ionised gas and rapid rotation around a central source—signs consistent with a growing black hole.
This result concerns one specific object and is based on spectroscopic observations. It does not automatically confirm the scenario proposed for 3DHST-AEGIS-12014, nor does it show that all little red dots are black holes. The two cases provide different pieces of evidence: one shows signs of accretion in a very ancient galaxy; the other combines the appearance of a little red dot with X-ray emission and variations that could reveal a hole-ridden veil of gas.
Future observations planned for the object detected by Chandra should help distinguish between the hypotheses. They may clarify the nature of the source and how its radiation is obscured. For astronomers, the stakes go beyond a single red dot: they need to understand whether these objects bear witness to a particular phase in black hole growth, and how that growth fits in with the growth of the first galaxies.
References
- NASA, ‘NASA Connects Little Red Dots with Chandra, Webb’
- ESA/Webb, ‘Webb witnesses a feasting supermassive black hole in the early Universe’
Mosaic of ‘little red dots’ and neighbouring galaxies in false colours, from a 2024 study. These examples are distinct from the object 3DHST-AEGIS-12014.
Credit: Jorryt Matthee and collaborators — Wikimedia Commons — CC BY 4.0.
