Evrim Yazgin
Cosmos science journalist
NASA’s space telescope Transiting Exoplanet Survey Satellite (TESS) has discovered a “hot Neptune desert” exoplanet in a tight orbit around its host star
The planet, TOI-3261 b, is only the fourth such planet found. Researchers say it’s an ideal candidate for studying how planets such as these form.
It’s behaviour is described in a paper published in the Astronomical Journal, fromanalysis led by Emma Nabbie, an astronomer at Australia’s University of Southern Queensland.
The system is 979 light-years from Earth. TOI-3261 b orbits an orange dwarf star every 21 hours at a distance of just 2.5 million km – about 60 times closer than Earth is to our Sun. This tight orbit puts the planet in exclusive company with only 3 other “ultra-short period (USP)” hot Neptunes whose masses have been precisely measured.
TOI-3261 b is about the size of Neptune, but twice as dense, making it about 30 times heavier than Earth.
The exoplanet could be a key to understanding how such USP gas giant planets form.
Computer modelling suggests the star and planet system is about 6.5 billion years old – about 2 billion years older than our solar system. TOI-3261 b probably started out as a much larger gas giant, but its lighter layers have been stripped away. This likely happened in two ways: photo-evaporation due to energy from its star, and gravitational forces from the star causing tidal stripping.
It’s also possible the planet formed further away from the star before edging closer. This may be why the planet retained its atmosphere, which has yet to be studied in detail.
“Atmospheric analysis of TOI-3261b would reveal a rich vault of information, potentially applicable to not only the handful of Neptune-sized USPs, but extending toward the general population of hot giant planet,” the authors write.
