A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system
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Seager, Sara![Thumbnail](/bitstream/handle/1721.1/148283/A_low-eccentricity_migration_pathway_for_a_13-h-pe.pdf.jpg?sequence=4&isAllowed=y)
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It is commonly accepted that exoplanets with orbital periods shorter than 1
day, also known as ultra-short period (USP) planets, formed further out within
their natal protoplanetary disk, 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 $\sim$ 13 hours, a
mass of 1.42 $\pm$ 0.18 M$_{\oplus}$, a radius of $1.166^{0.061}_{-0.058}$
R$_{\oplus}$, and a mean density of 4.89$^{+1.03}_{-0.88}$ gcm$^{-3}$. Via
Doppler spectroscopy, we discovered that the system hosts three outer planets
on nearly circular orbits with periods of 6.6, 26.2, and 61.3d and minimum
masses of 5.03 $\pm$ 0.41 M$_{\oplus}$, 33.12 $\pm$ 0.88 M$_{\oplus}$ and
15.05$^{+1.12}_{-1.11}$ M$_{\oplus}$, 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 Gyrs, starting from an initial orbit of
0.02au. TOI-500 is the first four planet system known to host a USP Earth
analog whose current architecture can be explained via a non-violent migration
scenario.
Date issued
2022Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary SciencesJournal
Nature Astronomy
Publisher
Springer Science and Business Media LLC
Citation
Seager, Sara. 2022. "A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system." Nature Astronomy, 6 (6).
Version: Author's final manuscript