If you thought planets only circled stars in neat, flat disks, think again. Scientists have uncovered compelling evidence for a bizarre kind of planet — one that loops around not just one, but two brown dwarfs, and does so in a radical orbit tilted almost 90 degrees to their own path.
This groundbreaking discovery, buried in the dance of celestial mechanics, suggests the first known case of a polar circumbinary planet — a planet that orbits a pair of stellar objects perpendicularly to their orbital plane. Although some astronomers suspected something like this can happen, this rewrites part of the rulebook on how planetary systems can form and behave.
“I am particularly excited to be involved in detecting credible evidence that this configuration exists,” says Thomas Baycroft, a PhD student at the University of Birmingham, UK, who led the study published today in Science Advances.
A needle in a cosmic haystack
Astronomers have found thousands of exoplanets — worlds beyond our solar system. Most of them are in single-star systems, like our own solar system. A few dozen orbit binary stars, dancing delicately around two suns. But the geometry is completely different. The new find breaks that mold. This planet doesn’t lie flat. It stands upright.
Located roughly 100 light-years away in the southern sky, the system known as 2MASS J15104786-2818174 — mercifully shortened to 2M1510 — contains two brown dwarfs. Brown dwarfs aren’t quite stars. They’re cosmic underachievers that never got massive enough to ignite nuclear fusion. The pair whirls around each other every 20.9 days, completing a tight, eccentric loop.
Just from this alone, this would be an extraordinary system, only the second system of this type ever discovered. But it also contains the first exoplanet ever found on a path at right angles to the orbit of its two host stars.
It gets even more interesting. The orbit’s orientation — the line connecting the closest and farthest points — shifts slowly over time in a process known as apsidal precession. In 2M1510, this precession is happening backward, and retrograde precession, as this called, is very unusual.
Simply put, this is a system that has not one but several very rare features.
What gave it away? A tiny wobble
Scientists spotted the planetary interloper not by seeing it directly, but by watching the brown dwarfs’ orbit change over time. Baycroft and team used data from the UVES instrument on the Very Large Telescope in Chile, tracking the radial velocity — the back-and-forth wobble — of each brown dwarf. The precision was stunning: 47 meters per second, or just over 100 miles per hour, despite the faintness of the stars.
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Using powerful models and orbital simulations, they ruled out known causes — general relativity, tidal forces, a third star far out in the system, and even odd rotation effects. None could explain the rate or direction of the precession.
The only explanation left: a planet orbiting perpendicularly to the brown dwarf pair.
“We reviewed all possible scenarios, and the only one consistent with the data is if a planet is on a polar orbit about this binary,” says Baycroft.
A bit of luck can go a long way
The find challenges our assumptions about how planets form. Most models suggest planets coalesce from flat disks of dust and gas swirling around stars. But polar orbits require something very different — a warped or misaligned disk or some cosmic jostling that forced the planet into its odd trajectory.
Basically, this shows that planetary architecture can be sculpted by the complex gravitational ballet of binary stars and their disks. It hints at exotic pathways of formation and migration. In these, gas clouds twist and torque to produce orbits few thought possible. And it opens the door to a hidden population of planets we’ve simply been blind to — worlds not orbiting “around” in the usual sense, but “over” their stars in a cosmic cartwheel.
We don’t know how many other planets like this there could be around. Even this one was discovered rather fortunately.
“The discovery was serendipitous, in the sense that our observations were not collected to seek such a planet, or orbital configuration. As such, it is a big surprise,” says Triaud. “Overall, I think this shows to us astronomers, but also to the public at large, what is possible in the fascinating universe we inhabit.”
Because the planet hasn’t been directly seen, we don’t know its exact size or composition. But even so, we know enough about it to know it’s a stunning find. With this new polar planet, we’re reminded that nature doesn’t always color inside the lines. Planets don’t always orbit like clock hands. Some dance sideways, boldly defying cosmic expectations.