NASA has identified TOI-3261 b, a Neptune-sized exoplanet with an ultra-short orbital period of just 21 Earth hours. Orbiting extremely close to its star, this “hot Neptune” belongs to a rare class of planets characterized by their small size and blistering proximity to their host stars. This discovery adds to the limited catalog of such planets, with only three other known examples.
The planet was discovered using NASA’s Transiting Exoplanet Survey Satellite (TESS), supported by ground-based observations from telescopes in Australia, Chile, and South Africa. Scientists reconstructed the history of this system, suggesting that TOI-3261 b might have started as a gas giant similar to Jupiter but underwent significant changes over billions of years.
TOI-3261 b likely experienced mass loss through processes such as photoevaporation, where stellar radiation eroded its atmosphere, and tidal stripping, where gravitational forces removed layers of gas. Alternatively, the planet might have formed farther from its star and later migrated inward, exposing it to intense stellar forces.
The planet’s high density—twice that of Neptune—indicates a remnant atmosphere stripped of lighter elements. Heavier gases dominate the remaining envelope, offering valuable clues about the processes shaping its evolution and atmosphere.
Further research could unlock the mysteries of TOI-3261 b’s composition. Astronomers propose using infrared observations with NASA’s James Webb Space Telescope to detect molecular signatures in its atmosphere, shedding light on its origins and the broader dynamics of hot giant planets.