Gj 3090 b exoplanet discovered with retrograde orbit

Astronomers have discovered Gj 3090 b, an exoplanet that orbits its host star in a retrograde direction. This sub-Neptune planet moves in the opposite direction to the rotation of its parent M-type dwarf star, making it the first known planet of this kind to orbit such a star.

Gj 3090 b has a radius approximately 2.2 times that of Earth and a mass 4.5 times greater. It completes an orbit every 2.9 days. The planet's orbital axis forms an angle of about 136 degrees with the star's rotation axis, confirming its retrograde trajectory. Researchers suggest this unusual orientation may be a legacy of the original protoplanetary disk.

The study, led by Yann Carteret of the University of Geneva and published in Astronomy & Astrophysics, utilized observations from the European Southern Observatory (ESO) in Chile. Scientists employed the Nirps and Harps spectrographs on the ESO 3.6-meter telescope to analyze the planet's transits using the Rossiter-McLaughlin effect.