Astronomers Found a Planet Orbiting the 'Wrong' Way — And It Shouldn't Exist
A newly discovered exoplanet is orbiting its star backwards and tilted almost completely sideways, and scientists say it shouldn't be possible under current planet-formation theories.
Somewhere 73 light-years from Earth, there's a planet that appears to be breaking the rules astronomers thought governed how solar systems come together. Researchers using the NIRPS instrument at Chile's La Silla Observatory have confirmed that an exoplanet called GJ 3090 b is orbiting its star backwards — and at an angle so extreme that scientists are scrambling to explain how it got that way.
Meet the Planet That Won't Play by the Rules
GJ 3090 b is a sub-Neptune, a planet type more common across the Milky Way than anything in our own solar system. It's about 2.2 times the radius of Earth and roughly 4.5 times as massive, orbiting a red dwarf star known as GJ 3090 that was itself only discovered in 2022. On paper, none of that sounds particularly unusual — sub-Neptunes are one of the most frequently detected categories of exoplanet.
What makes GJ 3090 b remarkable is its orbit. Most planets form from a disk of gas and dust that spins in the same direction as its parent star's rotation, so planets typically end up orbiting "with" their star rather than against it. GJ 3090 b does the opposite: it's in a full retrograde orbit, moving in the reverse direction of its star's spin.
A Tilt That Shouldn't Be Possible
Astronomers measure orbital misalignment using something called the Psi angle — essentially, how far off a planet's orbital plane is from its star's equatorial plane. A Psi of zero would mean a perfectly aligned orbit. GJ 3090 b clocks in at a staggering 136 degrees, meaning it's not just tilted, it's tilted past perpendicular and heading toward fully backwards.
According to the research team from the Université de Genève — Yann Carteret, Léna Parc, and Vincent Bourrier — only a handful of known planetary systems show a Psi angle greater than 70 degrees, and in every other known case, there's a massive companion object nearby whose gravity can explain the tilt. GJ 3090 b has no such companion. Whatever knocked this planet onto its rebellious path did so without an obvious culprit.
Why This Matters for Planet Formation Theory
The standard model of planet formation assumes a single, star-aligned disk of material from which planets gradually accrete. GJ 3090 b's misalignment suggests something messier might be going on in some systems — for instance, a star could accumulate a second, misaligned disk of gas and dust later in its life, with planets like GJ 3090 b forming from that secondary material instead of the original one.
If that theory holds up, it would mean the neat, tidy picture of planet formation — where everything settles into a flat, aligned disk — is more of a general tendency than a hard rule. Some solar systems, it turns out, might be shaped by a much more chaotic and layered process than previously assumed.
What Comes Next
The findings, published in Astronomy & Astrophysics on September 21, 2026, are likely to trigger a wave of follow-up observations aimed at finding more examples of extreme misalignment among sub-Neptunes specifically, since that planet class is so common yet still relatively poorly understood in terms of its orbital dynamics. Researchers will also be looking for any faint evidence of a second disk or a since-vanished companion object that could account for GJ 3090 b's strange path.
For now, GJ 3090 b stands as one of the most extreme examples of orbital rebellion ever recorded — a reminder that even in a galaxy where planet-hunting has become almost routine, the universe still has plenty of room to surprise us.
