Warm terrestrial planet with half the mass of Venus transiting a nearby star

Demangeon, O. D. S.; Zapatero Osorio, M. R.; Alibert, Y.; Barros, S. C. C.; Adibekyan, V.; Tabernero, H. M.; Antoniadis-Karnavas, A.; Camacho, J. D.; Suárez Mascareño, A.; Oshagh, M.; Micela, G.; Sousa, S. G.; Lovis, C.; Pepe, F. A.; Rebolo, R.; Cristiani, S.; Santos, N. C.; Allart, R.; Allende Prieto, C.; Bossini, D.; ... (2021). Warm terrestrial planet with half the mass of Venus transiting a nearby star. Astronomy and astrophysics, 653(A41), A41. EDP Sciences 10.1051/0004-6361/202140728

2108.03323.pdf - Submitted Version
Available under License Creative Commons: Attribution-Noncommercial-No Derivative Works (CC-BY-NC-ND).

Download (5MB) | Preview
[img] Text
aa40728-21.pdf - Published Version
Restricted to registered users only
Available under License Publisher holds Copyright.

Download (6MB) | Request a copy

The advent of a new generation of radial velocity instruments has allowed us to break the one Earth-mass barrier. We report a new milestone in this context with the detection of the lowest-mass planet measured so far using radial velocities: L 98-59 b, a rocky planet with half the mass of Venus. It is part of a system composed of three known transiting terrestrial planets (planets b to d). We announce the discovery of a fourth nontransiting planet with a minimum mass of 3.06_{-0.37}^{+0.33} MEarth and an orbital period of 12.796_{-0.019}^{+0.020} days and report indications for the presence of a fifth nontransiting terrestrial planet. With a minimum mass of 2.46_{-0.82}^{+0.66} MEarth and an orbital period 23.15_{-0.17}^{+0.60} days, this planet, if confirmed, would sit in the middle of the habitable zone of the L 98-59 system.
L 98-59 is a bright M dwarf located 10.6 pc away. Positioned at the border of the continuous viewing zone of the James Webb Space Telescope, this system is destined to become a corner stone for comparative exoplanetology of terrestrial planets. The three transiting planets have transmission spectrum metrics ranging from 49 to 255, which makes them prime targets for an atmospheric characterization with the James Webb Space Telescope, the Hubble Space Telescope, Ariel, or ground-based facilities such as NIRPS or ESPRESSO. With an equilibrium temperature ranging from 416 to 627 K, they offer a unique opportunity to study the diversity of warm terrestrial planets.
L 98-59 b and c have densities of 3.6_{-1.5}^{+1.4} and 4.57_{-0.85}^{+0.77} this http URL^{-3}, respectively, and have very similar bulk compositions with a small iron core that represents only 12 to 14 % of the total mass, and a small amount of water. However, with a density of 2.95_{-0.51}^{+0.79} this http URL^{-3} and despite a similar core mass fraction, up to 30 % of the mass of L 98-59 d might be water.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences > Theoretical Astrophysics and Planetary Science (TAPS)

UniBE Contributor:

Alibert, Yann Daniel Pierre, Haldemann, Jonas


500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering
500 Science




EDP Sciences




Janine Jungo

Date Deposited:

28 Mar 2022 14:51

Last Modified:

05 Dec 2022 16:12

Publisher DOI:


ArXiv ID:






Actions (login required)

Edit item Edit item
Provide Feedback