A Planet Rolling Against the Stellar Current express
The carousel spins all the horses in one direction, but one stubbornly gallops against the flow. That's exactly how the planet TOI-1710 b behaves around its star. Using the HARPS-N and GIANO-B instruments, astronomers measured its tilt at 149 degrees. That's nearly a 180-degree flip, meaning the planet orbits "backward" relative to the star's rotation.
Where did this flip come from? Most likely, the system's past resembled a chaotic intersection without traffic lights. Gravitational kicks from other planets (so-called planet-planet scattering) could have knocked TOI-1710 b off its normal orbit. Then the Kozai-Lidov mechanism kicked in: if a massive body is nearby, the planet's orbit starts to wobble like a pendulum, changing its tilt and eccentricity. In the end, tidal forces from the star rounded the orbit, but the tilt remained.
This discovery is important for understanding the "childhood" of planetary systems. Previously, it was thought that in the region where TOI-1710 b resides (the so-called savanna — the gap between rocky and gas planets), such violent migrations are rare. Now it's clear: even here, traces of real planetary catastrophes can hide.
The star TOI-1710 completes a full rotation on its axis in 21.5 days — about three Earth weeks. In that time, its planet only manages to cover a small part of its 24-day orbit.
In Frederick Pohl's novel "Gateway," the protagonists find an alien ship on a retrograde orbit, and it's the first sign that something is wrong with the system.