Astronomers Discover Exoplanet Orbiting Its Star in the Opposite Direction
World
Astronomers have determined that the exoplanet GJ 3090 b orbits its host star in the opposite direction to the star’s rotation. Its retrograde orbit is tilted by about 136 degrees, making the system an unusual case for studying how planets form around red dwarf stars.
The international team’s study was published on September 21, 2026, in Astronomy & Astrophysics. Researchers analyzed 23 hours of observations obtained with instruments installed on the 3.6-meter telescope at the La Silla Observatory in Chile. The NIRPS spectrograph enabled them to determine the three-dimensional orientation of GJ 3090 b’s orbit and confirm its retrograde motion.
Discovered in 2022, GJ 3090 b is the innermost planet in its system. It completes an orbit around its small red star in about 2.9 days. The system is currently understood to contain two or possibly three planets smaller than Neptune, each completing an orbit in less than 16 days.
Stars and planets generally form from the same rotating disk of gas and dust. As a result, planets typically orbit in the same direction as their host stars rotate. GJ 3090 b appears to be an exception, moving in the opposite direction.
Researchers also found no evidence of a massive object, such as another star or a large planet, that could have significantly altered GJ 3090 b’s orbit. This distinguishes the system from other known examples of strongly misaligned planetary orbits.
The researchers suggest that the unusual configuration may have emerged during the system’s formation. One possibility is that the young star accreted an additional disk of gas and dust oriented differently and moving in a retrograde direction. Planets could then have formed within that secondary disk with an unusual orbital orientation.
Vincent Bourrier, an astronomer at the University of Geneva and co-author of the study, said: “In the case of GJ 3090, the star could have accreted a misaligned, retrograde secondary disc in which the planets in the system then formed.”
The discovery provides a new opportunity to investigate how the environment surrounding young stars may influence planetary system architecture, particularly around red dwarf stars.
Discovered in 2022, GJ 3090 b is the innermost planet in its system. It completes an orbit around its small red star in about 2.9 days. The system is currently understood to contain two or possibly three planets smaller than Neptune, each completing an orbit in less than 16 days.
Stars and planets generally form from the same rotating disk of gas and dust. As a result, planets typically orbit in the same direction as their host stars rotate. GJ 3090 b appears to be an exception, moving in the opposite direction.
Researchers also found no evidence of a massive object, such as another star or a large planet, that could have significantly altered GJ 3090 b’s orbit. This distinguishes the system from other known examples of strongly misaligned planetary orbits.
The researchers suggest that the unusual configuration may have emerged during the system’s formation. One possibility is that the young star accreted an additional disk of gas and dust oriented differently and moving in a retrograde direction. Planets could then have formed within that secondary disk with an unusual orbital orientation.
Vincent Bourrier, an astronomer at the University of Geneva and co-author of the study, said: “In the case of GJ 3090, the star could have accreted a misaligned, retrograde secondary disc in which the planets in the system then formed.”
The discovery provides a new opportunity to investigate how the environment surrounding young stars may influence planetary system architecture, particularly around red dwarf stars.
Powered by Froala Editor