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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Abstract

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 https://www.nature.com/articles/s41550-022-01641-y. 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
URI: https://eprints.keele.ac.uk/id/eprint/10928

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