Serrano, LM, Gandolfi, D, Mustill, AJ, Barragán, O, Korth, J, Dai, F, Redfield, S, Fridlund, M, Lam, KWF, Díaz, MR, Grziwa, S, Collins, KA, Livingston, JH, Cochran, WD, Hellier, C, Bellomo, SE, Trifonov, T, Rodler, F, Alarcon, J, Jenkins, JM, Latham, DW, Ricker, G, Seager, S, Vanderspeck, R, Winn, JN, Albrecht, S, Collins, KI, Csizmadia, S, Daylan, T, Deeg, HJ, Esposito, M, Fausnaugh, M, Georgieva, I, Goffo, E, Guenther, E, Hatzes, AP, Howell, SB, Jensen, ELN, Luque, R, Mann, AW, Murgas, F, Osborne, HLM, Palle, E, Persson, CM, Rowden, P, Rudat, A, Smith, AMS, Twicken, JD, Van Eylen, V and Ziegler, C (2022) A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system. Nature Astronomy. ISSN 2397-3366

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It is commonly accepted that exoplanets with orbital periods shorter than one day, also known as ultra-short-period (USP) planets, formed further out within their natal protoplanetary disks before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here we present the discovery of a four-planet system orbiting the bright (V = 10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of ~13 hours, a mass of 1.42 ± 0.18 M⊕, a radius of 1.166+0.061−0.058R⊕ and a mean density of 4.89+1.03−0.88gcm−3. Via Doppler spectroscopy, we discovered that the system hosts 3 outer planets on nearly circular orbits with periods of 6.6, 26.2 and 61.3 days and minimum masses of 5.03 ± 0.41 M⊕, 33.12 ± 0.88 M⊕ and 15.05+1.12−1.11M⊕, respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2 Gyr, starting from an initial orbit of 0.02 au. TOI-500 is the first four-planet system known to host a USP Earth analogue whose current architecture can be explained via a non-violent migration scenario.

Item Type: Article
Additional Information: This is the accepted author manuscript (AAM). The final published version (version of record) is available online via Springer at Please refer to any applicable terms of use of the publisher.
Subjects: Q Science > QB Astronomy
Q Science > QB Astronomy > QB460 Astrophysics
Q Science > QB Astronomy > QB600 Planets. Planetology
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Depositing User: Symplectic
Date Deposited: 17 May 2022 15:20
Last Modified: 28 Oct 2022 01:30

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