NASA Discovers Rare Neptune-Sized Planet Where A Year Only Lasts 21 Hours

NASA scientists have discovered an exoplanet named TOI-3261 b, where a year lasts just 21 Earth hours. 

This ultra-hot planet is about the same size as our own Neptune, but orbits its star at an incredibly close distance, resulting in its extremely short year. Only the fourth object of its kind ever found, the planet could reveal clues as to how planets such as these form, NASA said.

The discovery was made using NASA's Transiting Exoplanet Survey Satellite (TESS), with follow-up observations from ground-based telescopes in Australia, Chile, and South Africa. The measurements revealed that this exoplanet belongs to a rare category known as "hot Neptunes," which are characterized by their small size, proximity to their star, and extremely short orbital periods. In the case of TOI-3261 b, a "year" lasts only 21 hours, earning it a spot in an exclusive group of ultra-short-period hot Neptunes, with only three other known members.

Through advanced modelling, the scientific team reconstructed the 6.5 billion-year history of the star and planet system. Their findings suggest that TOI-3261 b originated as a massive gas giant, possibly similar to Jupiter, but underwent significant transformation.

The planet likely lost substantial mass due to two primary mechanisms: photoevaporation, where stellar energy dispersed gas particles, and tidal stripping, where the star's gravitational force stripped away layers of gas. Alternatively, the planet may have formed at a greater distance from its star, where these effects would have been less pronounced, potentially allowing it to retain its atmosphere.

The remaining atmosphere of the planet, one of its most interesting features, will likely be the subject of further analysis. Notably, TOI-3261 b boasts a density twice that of Neptune, indicating that its atmosphere has been stripped of lighter elements over time, leaving behind only the heavier components.

This suggests that the planet's atmosphere once comprised a diverse range of elements, but the exact composition remains unknown. To unravel this mystery, astronomers propose observing the planet in infrared light, potentially utilisng NASA's James Webb Space Telescope. This approach would enable researchers to identify the distinctive molecular fingerprints in the planet's atmosphere, ultimately illuminating not only the past of TOI-3261 b but also the underlying physical processes governing all hot, giant planets.