Scientists find weird exoplanet that orbits its star in the wrong direction

Key Points:

• Scientists have discovered that the exoplanet GJ 3090 b, located about 73 light-years away, orbits its red dwarf host star in a highly misaligned and retrograde direction, meaning it rotates opposite to the star's rotation.
• This unusual orbital behavior is surprising because GJ 3090 b appears to be a singleton planet with no massive companion, such as a gas giant or brown dwarf, which typically explains such misalignments.
• The planet, classified as a sub-Neptune with a radius 2.2 times and mass 4.5 times that of Earth, exhibits an extraordinary Psi angle of 136 degrees, indicating a significant tilt between its orbital plane and the star's equatorial plane.
• The discovery was made possible by the precision of the NIRPS instrument at La Silla Observatory, which can measure such angles even for relatively small planets like GJ 3090 b.
• Researchers suggest alternative explanations for this anomaly, including the possibility that the star may have accreted a misaligned, retrograde secondary disk from which the planet formed, challenging existing models of planetary system formation.