2025/11/17 by Alves, Douglas R., Jenkins, James S., Vinés, José I. +29
#Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2511.13832
Observations have shown that planets similar to Neptune are rarely found orbiting Sun-like stars with periods up to ~4 days, defining the so-called Neptune desert region. Therefore, the detection of each individual planet in this region holds a high value, providing detailed insights into how such a population came to form and evolve. Here we report the detection of TOI-333b, a Neptune desert planet with a mass, radius, and bulk density of 20.1 ± 2.4 M⊕, 4.26 ± 0.11 R⊕, and 1.42 ± 0.21 \gccc, respectively. The planet orbits a F7V star every 3.78 d, whose mass, radius and effective temperature are of 1.2 ± 0.1 \msun, 1.10 ± 0.03 \rsun, and 6241+73-62 K, respectively. TOI-333b is likely younger than 1 Gyr, which is supported by the presence of the doublet Li line around 6707.856 textup~Å and its comparison to Li abundances in open clusters with well constrained ages. The planet is expected to host only 8.5+10.9-8.3% gas-to-core mass ratio for a H/He envelope. On the other hand, irradiated ocean world models predict 20+11-10% H2O mass fraction with a core fraction of 35+20-23%. Therefore, we expect that TOI-333b internal composition may be dominated by a pure rocky composition with almost no H/He envelope, or a rocky world with almost equal mass fraction of water. Finally, TOI-333b is more massive and larger than 77% and 82% of its Neptune desert counterparts, respectively, while its host ranks among the hottest known for Neptune Desert planets, making this system a unique laboratory to study the evolution of such planets around hot stars.