TOI-1710 A b orbits in the opposite direction to its star's spin, revealing a rare anti-aligned system

Star system: TOI 1710 | Distance from the Sun: 265 light years

TOI-1710 A b is a warm Neptune-sized planet that orbits its star in the opposite direction to the star's rotation, a configuration known as anti-alignment. This rare arrangement was discovered using the Rossiter-McLaughlin effect, which measures how the planet's transit affects the star's light. The planet's orbit is almost exactly opposite to the star's spin, with a true obliquity of about 158 degrees.

The host star has a distant M-dwarf companion, but this companion is too far away to have caused the planet's unusual orbit on its own. However, the star also shows signs of another, closer companion, likely a giant planet about five times the mass of Jupiter on a 15-au orbit. This intermediate companion could have dynamically linked the warm Neptune to the distant M dwarf, transferring the tilt from the wide binary orbit to the planet's orbit.

This discovery provides new insight into how planetary orbits can become misaligned, especially in systems with multiple companions. It shows that even planets around relatively quiet stars can have complex orbital histories shaped by interactions with other objects in the system.

Key findings
- TOI-1710 A b orbits in the opposite direction to its star's spin
- The system likely contains a distant M-dwarf and a closer giant planet
- Orbital tilt may be transferred through dynamical coupling
- Anti-aligned orbits are rare among known exoplanets
- Results help explain how planetary orbits can become misaligned

Scientific study

POSEIDON II: The Anti-Aligned Orbit of the Warm Neptune TOI-1710 A b (external link)