The JWST was built with the ability to observe the redshifted light of objects in the very early universe. Once operational, the telescope virtually deluged us with surprising, theory-challenging observations from the earliest ages of the universe. Some ancient galaxies were much larger and fully formed than previously thought. This also applied to their supermassive black holes (SMBH).
Now astronomers working with the Webb have found another mysterious early galaxy from when the universe was only 800 million years old. It’s a classic Jekyll and Hyde situation. When viewed in optical and ultraviolet light, it looks largely the same as most other galaxies. But when the JWST observed it in infrared, it appeared as a rampaging, ravenous animal.
The galaxy is called Virgil and is one of the Little Red Dots, a class of objects discovered by JWST. The telescope found more than 300 of them. They existed between about 600 million and 1.6 billion years after the Big Bang, with most concentrated in the earlier part of this range. They are at the edge of the JWST’s range and are very difficult to observe. Virgil is the reddest of the LRDs discovered to date.
Astrophysicists want to know what happened to the LRDs. Apparently they were abundant in the early universe, particularly around 600 million light-years after the Big Bang, but then mostly disappeared around 1.6 billion years after the Big Bang. There are various theories about what happened to them. The leading theory concerns the evolution of the universe and the dark matter it contains. As the universe evolved, dark matter halos grew larger and gained angular momentum, making it difficult for LRDs to form. They most likely evolved into the galaxies we see around us today.
The new observations of Virgil are part of a research paper published in the Astrophysical Journal entitled “Deciphering the Nature of Virgil: An Obscure Active Galactic Nucleus Lurking in an Apparently Normal Lyα Emitter During Cosmic Reionization.” The lead author is Pierluigi Rinaldi, now of the Space Telescope Science Institute but formerly at the Steward Observatory at the University of Arizona.
“Since its inception, JWST has pushed the boundaries of the redshift limit and made groundbreaking discoveries at very high redshift,” the authors write. The authors point to the discovery of Extremely Red Objects (ERO), of which LRDs are a special type. “The study of these sources and their nature has resulted in a huge amount of literature in a very short period of time,” the authors explain.
*These are 20 of the Little Red Dot galaxies discovered with the JWST. Their discovery was first announced in March 2024. Photo credit: Jorryt Matthee et al. 2024 ApJ 963 129DOI: 10.3847/1538-4357/ad2345URL: https://iopscience.iop.org/article/10.3847/1538-4357/ad2345, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=154052277*
“JWST showed that our ideas about how supermassive black holes formed were pretty much completely wrong,” said co-author George Rieke, Regents Professor of Astronomy and pioneer of infrared astronomy. “It looks like the black holes are actually ahead of the galaxies in many cases. That’s the most exciting thing about what we find,” Rieke said in a press release.
JWST’s near-infrared camera (NIRCam) or near-infrared spectrograph (NIRSpec) can only observe optical wavelengths at this early point in the history of the universe. These observations show that it is a relatively normal, star-forming galaxy with an appropriately sized black hole at its center. But JWST’s MIRI (Mid-Infrared Instrument) can see infrared light from this era. The MIRI observations penetrated the dust surrounding Virgil and revealed his true nature. It hosts a supermassive black hole that is heavily obscured by dust and releases enormous amounts of energy as it feeds.
When SMBH actively accumulate matter, they are called active galactic nuclei (AGN). As AGN attracts matter, it collects in a rotating accretion ring. The gas and dust in the ring heat up and release high-energy light. Light from distant, ancient AGN like Virgil is extremely redshifted and detectable by JWST.
“Virgil has two personalities,” Rieke said. “The UV light and optics show its ‘good’ side – a typical young galaxy quietly forming stars. But when MIRI data is added, Virgil turns into the host of a heavily obscured supermassive black hole, emitting immense amounts of energy.”
“With MIRI we can fundamentally observe beyond what we can detect with UV and optical wavelengths,” said lead author Rinaldi, whose doctoral thesis focused on MIRI observations. “It’s easy to observe stars because they shine and grab our attention. But there is more than just stars, something only MIRI can reveal.”
MIRI requires more time to capture deep images than the other JWST instruments. This means that many of the JWST surveys are carried out using NIRCam and NIRSpec, which requires less time. As a result, there could be many more objects like Virgil out there, heavily obscured by dust, whose true nature can only be revealed through longer exposure times using MIRI. There may be a significant population of these types of LRDs that scientists are unaware of. If so, they may have played a larger role in the evolution of the cosmos than previously thought. They could be associated with the cosmic dawn, when the universe re-ionized just about 200 million years after the Big Bang.
But the researchers point out how complex the object is and how difficult it is to determine its true nature. “By comparing the UV- and Hα-based SFRs, we find that Virgil may be entering or fading out of an explosive phase,” they write. This suggests a “…limited role in cosmic reionization,” you explain, although “Virgil’s overall spectral properties are consistent with the average galaxy population during the EoR.”
Researchers aren’t sure if what they’re seeing is an AGN. Some diagnostics indicate that it is an AGN typical of people with high redshifts, “but when redshift evolution is taken into account, its classification becomes ambiguous,” they write. It can be difficult to separate the light from star formation from that of an AGN.
However, at the end of their analysis they choose the AGN explanation. “Although modeling this source remains challenging, our results show that the adjustments consistently require the presence of a dust-obscured AGN, consistent with the findings of E. Iani et al. (2025),” they explain.
In any case, the authors write that Virgil is one of the most extreme LRDs found to date.
The fact that no other LRDs like Virgil have been discovered is likely due to observational errors, according to the researchers. “Are we simply blind to its siblings because equally deep MIRI data over larger regions of the sky have not yet been obtained?” Rinaldi asked.
The researchers want to find out by carrying out further long-term exposure observations with the JWST’s MIRI. As they find more of them, a narrative will emerge that places LRDs in the context of the evolution of the universe.
“JWST will have a fascinating story to tell as it slowly peels back the obfuscations into a common narrative,” Rinaldi said.
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