An international team of scientists has discovered a new Neptune-sized exoplanet, designated TOI-3261 b, which orbits extremely close to its host star, completing a revolution in just 21 hours. This finding, made using NASA's Transiting Exoplanet Survey Satellite (TESS) and subsequent observations from ground-based telescopes in Australia, Chile, and South Africa, adds to the rare category of 'hot Neptunes'—a term used for planets similar in size to Neptune but with significantly higher temperatures.
TOI-3261 b is only the fourth of its kind identified, placing it in what researchers describe as the 'hot Neptune desert,' a region of parameter space where such planets are scarce. The discovery is significant as it may provide clues to the processes of planetary formation and evolution, particularly for gas giants that orbit close to their stars.
The planet is believed to have started as a larger gas giant, likely losing much of its mass through mechanisms such as photoevaporation and tidal stripping due to the intense gravitational forces and energy emitted by its star. Current models suggest that the TOI-3261 b system is approximately 6.5 billion years old, emphasizing the planet's long history of atmospheric loss.
One of the most intriguing aspects of TOI-3261 b is its remaining atmosphere, which is denser than Neptune's, indicating that lighter gases have been stripped away over time. Future observations, particularly in infrared light using NASA's James Webb Space Telescope, could reveal the chemical composition of this atmosphere, shedding light on the planet's formation history and the characteristics of hot giant planets in general.
The research team, led by astronomer Emma Nabbie from the University of Southern Queensland, published their findings in The Astronomical Journal. This discovery not only enhances our understanding of exoplanetary atmospheres but also contributes to the broader knowledge of planetary formation mechanisms across the universe.