Observations have shown that planets similar to Neptune are rarely found orbiting Sun-like stars with periods up to ∼4 days. This defines the so-called Neptune desert region. The detection of each individual planet in this region therefore holds a high value by providing detailed insights into the formation and evolution of this population. 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 g cm-3. The planet orbits an F7V star every 3.78 d, whose mass, radius, and effective temperature are of 1.2 ± 0.1 M⊙, 1.10 ± 0.03 R⊙, and 6241-62+73 K, respectively. TOI-333bis likely younger than 1 Gyr, which is supported by the doublet Li line around 6707.856 Éand its comparison to Li abundances in open clusters with well-constrained ages. The planet is expected to host only a 8.5-8.3+10.9% gas-to-core mass ratio for an H/He envelope. On the other hand, models of irradiated ocean worlds predict a 20-10+11% H2O mass fraction with a core fraction of 35-23+20%. We therefore expect that the internal composition of TOI-333bis 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-333bis more massive and larger than 77% and 82% of its Neptune-desert counterparts, and its host ranks among the hottest known stars for Neptune-desert planets. This makes this system a unique laboratory for studying the evolution of these planets around hot stars.
TOI-333b: A Neptune-desert planet around an F7V star / Alves, D.R., Jenkins, J.S., Vinés, J.I., Moyano, M., Anderson, D.R., Magliano, C., Covone, G., Stassun, K.G., Soubkiou, A., Gillen, E., Battley, M.P., Hughes, A., Armstrong, D.J., Saha, S., Hawthorn, F., Wheatley, P.J., Collins, K.A., Schwarz, R.P., Srdoc, G., Apergis, I., et al.. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 1432-0746. - 705:(2026). [10.1051/0004-6361/202557014]
TOI-333b: A Neptune-desert planet around an F7V star
Christian Magliano;Giovanni Covone;
2026
Abstract
Observations have shown that planets similar to Neptune are rarely found orbiting Sun-like stars with periods up to ∼4 days. This defines the so-called Neptune desert region. The detection of each individual planet in this region therefore holds a high value by providing detailed insights into the formation and evolution of this population. 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 g cm-3. The planet orbits an F7V star every 3.78 d, whose mass, radius, and effective temperature are of 1.2 ± 0.1 M⊙, 1.10 ± 0.03 R⊙, and 6241-62+73 K, respectively. TOI-333bis likely younger than 1 Gyr, which is supported by the doublet Li line around 6707.856 Éand its comparison to Li abundances in open clusters with well-constrained ages. The planet is expected to host only a 8.5-8.3+10.9% gas-to-core mass ratio for an H/He envelope. On the other hand, models of irradiated ocean worlds predict a 20-10+11% H2O mass fraction with a core fraction of 35-23+20%. We therefore expect that the internal composition of TOI-333bis 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-333bis more massive and larger than 77% and 82% of its Neptune-desert counterparts, and its host ranks among the hottest known stars for Neptune-desert planets. This makes this system a unique laboratory for studying the evolution of these planets around hot stars.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
