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A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system

Serrano, Luisa Maria and Gandolfi, Davide and Mustill, Alexander J. and Barragán, Oscar and Korth, Judith and Dai, Fei and Redfield, Seth and Fridlund, Malcolm and Lam, Kristine W. F. and Díaz, Matías R. and Grziwa, Sascha and Collins, Karen A. and Livingston, John H. and Cochran, William D. and Hellier, Coel and Bellomo, Salvatore E. and Trifonov, Trifon and Rodler, Florian and Alarcon, Javier and Jenkins, Jon M. and Latham, David W. and Ricker, George and Seager, Sara and Vanderspek, Roland and Winn, Joshua N. and Albrecht, Simon and Collins, Kevin I. and Csizmadia, Szilárd and Daylan, Tansu and Deeg, Hans J. and Esposito, Massimiliano and Fausnaugh, Michael and Georgieva, Iskra and Goffo, Elisa and Guenther, Eike and Hatzes, Artie P. and Howell, Steve B. and Jensen, Eric L. N. and Luque, Rafael and Mann, Andrew W. and Murgas, Felipe and Osborne, Hannah L. M. and Palle, Enric and Persson, Carina M. and Rowden, Pamela and Rudat, Alexander and Smith, Alexis M. S. and Twicken, Joseph D. and Van Eylen, Vincent and Ziegler, Carl (2022) A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system. Nature Astronomy, 6 (6). pp. 736-750. ISSN 2397-3366. doi:10.1038/s41550-022-01641-y.

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[img] PDF (The list of favourable targets for atmospheric analysis. TOI-500 b is ranked 8th) - Supplemental Material
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[img] PDF (HARPS RV measurements and activity indicators of TOI-500) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 1: Field of view with the locations of the 78 Gaia DR2 stars checked for NEBs) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 2: Gemini/Zorro 5-sigma contrast curve) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 3: SOAR contrast curve) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 4: Time series of the HARPS RV measurements) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 5: Generalized Lomb-Scargle periodograms of the HARPS SERVAL RV measurements and residuals) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 6: Generalized Lomb-Scargle periodograms of the activity indicators following the subtraction of the seasonal median values (see Methods)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 7: Lomb-Scargle periodograms of the WASP-South light curves of TOI-500) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 8: Median-subtracted HARPS SERVAL RVs (upper panel), S-index (middle panel), and FWHM (lower panel)) - Supplemental Material
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[img] Image (JPEG) (Extended Data Fig. 9: Scatter plot of exoplanets with atmospheric S/N ratio) - Supplemental Material
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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)_(−0.058) R⊕ and a mean density of 4.89^(+1.03)_(−0.88)g cm⁻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)_(−1.11) M⊕, 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
Related URLs:
URLURL TypeDescription ReadCube access Paper ItemMikulski Archive for Space Telescopes (MAST) ItemESO Science Archive Facility ItemExoplanet Follow-up Observing Program (ExoFOP) ItemGemini data
Serrano, Luisa Maria0000-0001-9211-3691
Gandolfi, Davide0000-0001-8627-9628
Mustill, Alexander J.0000-0002-2086-3642
Barragán, Oscar0000-0003-0563-0493
Korth, Judith0000-0002-0076-6239
Dai, Fei0000-0002-8958-0683
Redfield, Seth0000-0003-3786-3486
Fridlund, Malcolm0000-0003-2180-9936
Lam, Kristine W. F.0000-0002-9910-6088
Díaz, Matías R.0000-0002-2100-3257
Grziwa, Sascha0000-0003-3370-4058
Collins, Karen A.0000-0001-6588-9574
Livingston, John H.0000-0002-4881-3620
Cochran, William D.0000-0001-9662-3496
Hellier, Coel0000-0002-3439-1439
Trifonov, Trifon0000-0002-0236-775X
Rodler, Florian0000-0003-0650-5723
Alarcon, Javier0000-0003-0650-5723
Jenkins, Jon M.0000-0002-4715-9460
Latham, David W.0000-0001-9911-7388
Ricker, George0000-0003-2058-6662
Seager, Sara0000-0002-6892-6948
Vanderspek, Roland0000-0001-6763-6562
Winn, Joshua N.0000-0002-4265-047X
Albrecht, Simon0000-0003-1762-8235
Collins, Kevin I.0000-0003-2781-3207
Csizmadia, Szilárd0000-0001-6803-9698
Daylan, Tansu0000-0002-6939-9211
Deeg, Hans J.0000-0003-0047-4241
Esposito, Massimiliano0000-0002-6893-4534
Fausnaugh, Michael0000-0002-9113-7162
Georgieva, Iskra0000-0002-5056-1899
Goffo, Elisa0000-0001-9670-961X
Guenther, Eike0000-0002-9130-6747
Hatzes, Artie P.0000-0002-3404-8358
Howell, Steve B.0000-0002-2532-2853
Jensen, Eric L. N.0000-0002-4625-7333
Luque, Rafael0000-0002-4671-2957
Mann, Andrew W.0000-0003-3654-1602
Murgas, Felipe0000-0001-9087-1245
Osborne, Hannah L. M.0000-0002-4143-4767
Palle, Enric0000-0003-0987-1593
Persson, Carina M.0000-0003-1257-5146
Rowden, Pamela0000-0002-4829-7101
Smith, Alexis M. S.0000-0002-2386-4341
Twicken, Joseph D.0000-0002-6778-7552
Van Eylen, Vincent0000-0001-5542-8870
Ziegler, Carl0000-0002-0619-7639
Additional Information:© The Author(s), under exclusive licence to Springer Nature Limited 2022. Received 06 August 2021; Accepted 23 February 2022; Published 28 April 2022. This work was supported by the KESPRINT ( collaboration, an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. We acknowledge the use of TESS Alert data, which is currently in a beta test phase, from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing Program through the NASA Advanced Supercomputing Division at Ames Research Center for the production of the SPOC data products. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work makes use of observations made with the ESO 3.6 m telescope at the European Southern Observatory (ESO), La Silla, under ESO programmes 1102.C-0923, 0102.C-0338, 0103.C-0442, 0103.C-0548, 60.A-9700 and 60.A-9709. We are very grateful to the ESO staff members for their precious support during the observations. We warmly thank X. Dumusque and F. Bouchy for coordinating the shared observations with HARPS and J. Alvarado Montes, X. Delfosse, G. Gaisné, M. Hobson and D. Barrado Navascués, who helped collecting the HARPS spectra. This work has made use of data from the European Space Agency mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium ( Funding for the Data Processing and Analysis Consortium has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This work makes use of observations from the LCOGT network. LCOGT telescope time was granted by NOIRLab through the Mid-Scale Innovations Program, which is funded by the National Science Foundation. Some of the observations in the paper made use of the high-resolution imaging instrument Zorro. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by S. B. Howell, N. Scott, E. P. Horch and E. Quigley. Data was reduced using a software pipeline originally written by E. Horch and M. Everett. Zorro was mounted on the Gemini South telescope and the Near Infrared Imager (NIRI) was mounted on the Gemini North telescope, of the international Gemini Observatory, a programme of the National Science Foundation’s OIR Lab, which is managed by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil) and Korea Astronomy and Space Science Institute (Republic of Korea). Data collected under programme GN-2019A-LP-101. This work was based in part on observations obtained at the SOAR telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil, the US National Science Foundation’s NOIRLab, the University of North Carolina at Chapel Hill and Michigan State University. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. L.M.S. and D.G. gratefully acknowledge financial support from the CRT foundation under Grant No. 2018.2323 “Gaseous or rocky? Unveiling the nature of small worlds.” E.Gu. acknowledges the generous support by the Thüringer Ministerium für Wirtschaft, Wissenschaft und Digitale Gesellschaft. I.G., C.M.P., M.Fr. and A.J.M. gratefully acknowledge the support of the Swedish National Space Agency (DNR 174/18, 65/19, 120/19C). J.K. gratefully acknowledges the support of the Swedish National Space Agency (DNR 2020-00104). S.C., M.E., K.W.F.L., S.G. and A.P.H. acknowledge support by DFG grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, “Exploring the Diversity of Extrasolar Planets”. M.R.D. acknowledges the support by Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)-PFCHA/Doctorado Nacional-21140646, Chile. T.D. acknowledges support from MIT’s Kavli Institute as Kavli postdoctoral fellow. T.T. acknowledges support by the DFG Research Unit FOR 2544 “Blue Planets around Red Stars" project No. KU 3625/2-1. T.T. further acknowledges support by the BNSF programme “VIHREN-2021" project No. КП-06-ДВ/5. Data availability: TESS photometry is available at the Mikulski Archive for Space Telescopes (MAST) at under target name TOI-500.01. The raw HARPS spectra can be retrieved from the ESO Science Archive Facility ( under ESO programme IDs 1102.C-0923 (PI: D.G.), 0103.C-0442 (PI: M.R.D.), 0102.C-0338 and 0103.C-0548 (PI: T.T.), and 60.A-9700 and 60.A-9709 (ESO technical time). The ground-based photometry obtained with the LCO telescope, as well as the SOAR and Gemini imaging data, are available on the Exoplanet Follow-up Observing Program (ExoFOP) website ( under target name TOI-500.01. The raw Gemini data are available at under Program ID GS-2020A-Q-125. The archival WASP data that support the findings of this study are available from the co-author C. Hellier upon reasonable request ( The archival SOAR data that support the findings of this study are available from the co-author C. Ziegler ( upon reasonable request. The extracted radial velocities and stellar activity indicators are listed in Supplementary Data 2. Code availability: The numerical code used to test the low-eccentricity migration pathway is available via Zenodo at Contributions: L.M.S. performed the periodogram analysis and the joint analysis with pyaneti, wrote most of the text and coordinated the contributions from the other co-authors. D.G. performed the radial velocity analysis using the floating chunk offset method, wrote a significant part of the text and is the principal investigator of the HARPS large programme, which enabled the discovery of three additional planets and the determinations of the planetary (minimum) masses. O.B. performed the multi-dimensional Gaussian process analysis and wrote the relative section. J.K. ran the stability analyses with rebound and SPOCK and wrote the relative section. A.J.M. and F.D. described the most probable formation/migration processes of the system. A.J.M. also ran the numerical simulation to test the low-eccentricity migration pathway and wrote the relative section. M. Fridlund performed the spectral and chemical abundance analysis. K.W.F.L. and S.G. searched the TESS light curve for transit signals. K.A.C. performed the LCOGT observations and analysed the data. J.H.L. analysed the GEMINI and SOAR imaging data. J.A., M.R.D., F.R. and T.T. contributed to the HARPS RV follow-up. W.D.C. computed the probability that TOI-500 belongs to different stellar populations. C.H. analysed the WASP-South light curves. S.E.B. contributed to the analysis of the radial velocity data. S.R. explored the possibility to study the secondary atmosphere of TOI-550 b and wrote the relative section. S.A., S.C., H.J.D., M.E., I.G., E. Goffo, E. Guenther, A.P.H., R.L., F.M., H.L.M.O., E.P., C.M.P., A.M.S.S. and V.V.E. are members of the KESPRINT consortium and contributed to the HARPS large programme. C.Z. and A.W.M. performed the SOAR imaging observations. E.L.N.J. contributed to the LCOGT observations. S.B.H. performed the observations with GEMINI/ZORRO. J.M.J., D.W.L., G.R., S.S., R.V. and J.N.W. are the architects of the TESS mission. K.I.C., T.D., M. Fasnaugh, A.W.M., P.R., A.R. and J.D.T. significantly contributed to the success of the TESS mission, which discovered the USP planet candidate. All authors reviewed the manuscript. The authors declare no competing interests. Peer review information: Nature Astronomy thanks the anonymous reviewers for their contribution to the peer review of this work.
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
CRT Foundation2018.2323
Thüringer Ministerium für Wirtschaft, Wissenschaft und Digitale GesellschaftUNSPECIFIED
Swedish National Space AgencyDNR 174/18
Swedish National Space Agency65/19
Swedish National Space Agency120/19C
Swedish National Space AgencyDNR 2020-00104
Deutsche Forschungsgemeinschaft (DFG)RA714/14-1
Deutsche Forschungsgemeinschaft (DFG)SPP 1992
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)21140646
Kavli Institute for Cosmological PhysicsUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)KU 3625/2-1
Bulgarian National Science Fund (BNSF)КП-06-ДВ/5
Subject Keywords:Astronomy and astrophysics; Exoplanets
Issue or Number:6
Record Number:CaltechAUTHORS:20220504-142830436
Persistent URL:
Official Citation:Serrano, L.M., Gandolfi, D., Mustill, A.J. et al. A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system. Nat Astron 6, 736–750 (2022).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114573
Deposited By: Tony Diaz
Deposited On:04 May 2022 16:31
Last Modified:30 Jun 2022 17:47

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