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An illustration of a mysterious perturber discovered by astronomers through its gravitational effects. | Credit: Robert Lea (created with Canva)
A completely dark and mysterious body with a mass of 1 million suns and a possible black hole heart continues to perplex and intrigue astronomers despite further investigation.
This “mysterious disruptor” is about 11 billion light-years away and was discovered in 2025 due to its gravitational influence. It is now the most distant body ever detected due to its gravitational effects alone.
But astronomers are not complete in the dark about the mysterious disruptor, though. In fact, they are sure they know what lies at the heart of this strange cosmic body. “The inner core is consistent with a the black hole or dense stellar core, which surprisingly accounts for about a quarter of the object’s total mass,” explained Vegetti. “As we move away from the center, however, the object’s density flattens into a large disc-like component. This is a structure we have not seen before, so it could be a new class of dark objects.”
This strange structure was found in the gravitational lensing system JVAS B1938+666. Gravitational lensing is a phenomenon first predicted by Einstein in his 1915 theory of gravity known as general relativity. It occurs when light from a background source passes through the curvature of space caused by a massive object in the foreground, known as gravitational lensing, causing its usually straight path to become curved. The way light is affected not only allows objects to be seen at great distances by amplifying the light, but also tells scientists a lot about how mass is distributed within the lens system itself.
The JVAS B1938+666 gravitational lens consists of massive bodies ranging from 6.5 billion to 11 billion light-years away, including this “mysterious disruptor,” the most distant feature of Jvas B1938+666. A team of astronomers tried to reconstruct the mass distribution in the object, revealing the so-called “density profile”.
This is an extremely complex procedure, given that JVAS B1938+666 consists of many different bodies, the main component of which is a massive elliptical galaxy. Unlike those other bodies, however, the mysterious disruptor is completely invisible.
“Trying to separate all the different mass components of such a distant, low-mass object using gravitational lensing was extremely challenging and incredibly exciting,” team leader Simona Vegetti of the Max Planck Institute for Astrophysics, Germany, said in a statement. “We’re working with high-quality data and complex models, and just when we thought we had it all figured out, its properties threw up another surprise. It’s this combination of difficulty and mystery that makes this object so fascinating.”
What do we know so far about the mysterious disruptor?
To investigate the mysterious perturber, Vegetti and colleagues began analyzing the small perturbations, or perturbations, that it produces in the general arc of the gravitational lens JVAS B1938+666. They then compared the data collected by a number of telescopes, incl Green Bank Telescope, to various dark matter models. This revealed that none of these models could explain the mysterious disruptor.
“It has a very strange profile, because it is particularly dense at the center, but it expands enormously,” said team member Davide Massari of the National Institute of Astrophysics. “So it’s not uniformly distributed: it’s like there’s an extremely compact object in the center, but then the profile continues to extend to much greater distances than typically seen in galaxies or star systems of comparable mass.”
(Left) The gravitational arc of the JVAS B1938+666 system. The two “X’s” indicate the positions of two low-mass perturbers. (Right) The roughly one-million-solar-mass perturber. | Credit: DM Powell et al.
Although investigations into the mysterious disruptor have so far involved radio telescopes, future studies and a potential solution to this enigma could come thanks to telescopes operating in other wavelengths of light, including strong infrared vision of light. The James Webb Space Telescope (JWST). “If we were finally able to observe some form of light emission in the visible or infrared range, we could conclude, for example, that it is a somewhat anomalous ultracompact dwarf galaxy with an unusually extended stellar halo,” team member Cristiana Spingola from the National Institute of Astrophysics. “But if even with JWST we fail to see starlight or other visible matter, then it would mean that we are dealing with an object whose properties are difficult to explain with current dark matter models.”
The team’s research was published Monday (January 5) in the journal Astronomy of nature.