Astronomers have made an extraordinary discovery that could change the way we understand some of the most puzzling objects in the universe: brown dwarfs.
These so-called “failed stars” are larger than planets but too small to shine like stars, and they’ve long baffled scientists.
Now, researchers have identified a rare quadruple star system that includes not just two young red dwarfs, but also a pair of brown dwarfs.
The find offers a unique chance to unlock some of the mysteries surrounding these faint and elusive objects.
The system, named UPM J1040−3551 AabBab, lies just 82 light-years away in the constellation Antlia. It was uncovered by an international team led by Professor Zenghua Zhang of Nanjing University and described in the journal Monthly Notices of the Royal Astronomical Society.
What makes this system remarkable is its structure.
It’s not just a group of four stars clustered together—it’s a hierarchical quadruple system. This means there are two close pairs that orbit each other over vast timescales: the red dwarf pair (called Aab) and the brown dwarf pair (Bab).
Together, these pairs orbit around a common center of mass, completing one giant loop that takes more than 100,000 years.
Such stability is rare, and astronomers had to work carefully to prove these objects are indeed bound together.
They used data from the European Space Agency’s Gaia satellite and NASA’s Wide-field Infrared Survey Explorer (WISE) to measure their motion across the sky. Because the stars’ orbital dance unfolds over hundreds of millennia, scientists instead looked for a shared angular velocity—evidence that they are moving together through space.
Within the system, the red dwarf pair UPM J1040−3551 Aab shines brighter, though still faint by human standards.
These two stars are orange-hued, small, and cool compared to our sun, with surface temperatures of about 3,200 Kelvin (roughly 2,900°C). Each one is only about 17% as massive as the sun.
Despite their relative brightness compared to the brown dwarfs, the pair is around 100,000 times dimmer than Polaris, the North Star, and far too faint to see without a telescope.
The second pair, UPM J1040−3551 Bab, are true brown dwarfs—much cooler and dimmer than red dwarfs. They emit almost no visible light and can only be detected in infrared. One has a temperature of about 820 Kelvin (550°C), while the other is even cooler at 690 Kelvin (420°C). Both are classified as T-type brown dwarfs, making this the first known quadruple system in which such objects orbit two stars.
Although roughly the size of Jupiter, they are much more massive, weighing in at 10 to 30 times Jupiter’s mass.
The system was confirmed through detailed spectroscopic observations led by Dr. Felipe Navarete of Brazil’s National Astrophysics Laboratory, who used the Southern Astrophysical Research (SOAR) Telescope in Chile.
These observations revealed the distinct signatures of both the red dwarfs and the brown dwarfs, confirming their temperatures, brightness, and binary nature.
For scientists, the discovery is particularly exciting because it helps address what’s known as the “age-mass degeneracy problem” in brown dwarf research. Brown dwarfs cool over time, which makes it hard to know whether a faint, cool object is an old heavy brown dwarf or a young lightweight one.
When brown dwarfs are found in systems with stars whose ages can be measured independently, they provide crucial benchmarks. In this case, signs of activity in the red dwarf pair suggest the system is relatively young, somewhere between 300 million and 2 billion years old.
“This system is a goldmine,” said Professor Adam Burgasser of the University of California San Diego, a co-author of the study. “It allows us to test both atmospheric models, which describe how brown dwarfs look, and evolutionary models, which describe how they change over time.”
The team hopes that with future high-resolution imaging, they may be able to separate the brown dwarf pair visually and track their orbit. That would allow astronomers to measure their masses directly, giving even more insight into how these mysterious objects form and evolve.
As Professor Zhang explained, the discovery is not just about cataloging another unusual system but about opening a new cosmic laboratory. “This is the first quadruple system ever discovered with a pair of T-type brown dwarfs orbiting two stars,” he said. “It provides a unique opportunity to study both the nature of brown dwarfs and the ways in which complex stellar systems form.”
With each discovery like UPM J1040−3551, astronomers get closer to answering one of the great questions of the universe: where do brown dwarfs fit in the grand scheme of stars and planets? For now, this rare four-body dance offers a rare window into their hidden world.
Source: Royal Astronomical Society.
