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A 38 Million Year Old Neptune-sized Planet in the Kepler Field

Bouma, L. G. and Curtis, J. L. and Masuda, K. and Hillenbrand, L. A. and Stefánsson, G. and Isaacson, H. and Narita, N. and Fukui, A. and Ikoma, M. and Tamura, M. and Kraus, A. L. and Furlan, E. and Gnilka, C. L. and Lester, K. V. and Howell, S. B. (2022) A 38 Million Year Old Neptune-sized Planet in the Kepler Field. Astronomical Journal, 163 (3). Art. No. 121. ISSN 1538-3881. doi:10.3847/1538-3881/ac4966.

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Kepler 1627A is a G8V star previously known to host a 3.8 R⊕ planet on a 7.2 day orbit. The star was observed by the Kepler space telescope because it is nearby (d = 329 pc) and it resembles the Sun. Here, we show using Gaia kinematics, TESS stellar rotation periods, and spectroscopic lithium abundances that Kepler 1627 is a member of the 38⁺⁶₋₅ Myr old δ Lyr cluster. To our knowledge, this makes Kepler 1627Ab the youngest planet with a precise age yet found by the prime Kepler mission. The Kepler photometry shows two peculiarities: the average transit profile is asymmetric, and the individual transit times might be correlated with the local light-curve slope. We discuss possible explanations for each anomaly. More importantly, the δ Lyr cluster is one of ∼10³ coeval groups whose properties have been clarified by Gaia. Many other exoplanet hosts are candidate members of these clusters; their ages can be verified with the trifecta of Gaia, TESS, and ground-based spectroscopy.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Bouma, L. G.0000-0002-0514-5538
Curtis, J. L.0000-0002-2792-134X
Masuda, K.0000-0003-1298-9699
Stefánsson, G.0000-0001-7409-5688
Isaacson, H.0000-0002-0531-1073
Narita, N.0000-0001-8511-2981
Fukui, A.0000-0002-4909-5763
Ikoma, M.0000-0002-5658-5971
Tamura, M.0000-0002-6510-0681
Kraus, A. L.0000-0001-9811-568X
Furlan, E.0000-0001-9800-6248
Gnilka, C. L.0000-0003-2519-6161
Lester, K. V.0000-0002-9903-9911
Howell, S. B.0000-0002-2532-2853
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 October 12; revised 2021 December 6; accepted 2021 December 27; published 2022 February 9. The authors are grateful to J. Winn, J. Spake, A. Howard, and T. David for illuminating discussions and suggestions, and to R. Kerr for providing us with the Kerr et al. (2021) membership list prior to its publication. The authors are also grateful to K. Collins for helping resolve the scheduling conflict that would have otherwise prevented the MuSCAT3 observations. L.G.B. acknowledges support from a Charlotte Elizabeth Procter Fellowship from Princeton University, as well as from the TESS GI Program (NASA grant 80NSSC21K0335) and the Heising-Simons Foundation (51 Pegasi b Fellowship). Keck/NIRC2 imaging was acquired by program 2015A/N301N2L (PI: A. Kraus). In addition, this paper is based in part on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center and under financial support by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory. This work is partly supported by JSPS KAKENHI Grant Nos. 22000005, JP15H02063, JP17H04574, JP18H05439, and JP18H05442, JST PRESTO grant No. JPMJPR1775, and the Astrobiology Center of National Institutes of Natural Sciences (NINS; grant No. AB031010). This paper also includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission directorate. We thank the TESS Architects (G. Ricker, R. Vanderspek, D. Latham, S. Seager, and J. Jenkins) and the many TESS team members for their efforts to make the mission a continued success. Finally, this research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. We also thank the Keck Observatory staff for their support of HIRES and remote observing. We recognize the importance that the summit of Maunakea has within the indigenous Hawaiian community, and are deeply grateful to have the opportunity to conduct observations from this mountain. Software: altaipony (Ilin et al. 2021), astrobase (Bhatti et al. 2018), astropy (Astropy Collaboration et al. 2018), astroquery (Ginsburg et al. 2018), corner (Foreman-Mackey 2016), exoplanet (Foreman-Mackey et al. 2021), and its dependencies Agol et al. (2020); Kipping (2013); Luger et al. (2019); Theano Development Team (2016), PyMC3 (Salvatier et al. 2016), scipy (Jones et al. 2001), TESS-point (Burke et al. 2020), wotan (Hippke et al. 2019). Facility: Astrometry: Gaia (Gaia Collaboration et al. 2018b; Gaia Collaboration 2021a). Imaging: Second Generation Digitized Sky Survey. Keck:II (NIRC2; Gemini:North ('Alopeke; Scott et al. (2018, 2021). Spectroscopy: Keck:I (HIRES; Vogt et al. 1994). Photometry: Kepler (Borucki et al. 2010), MuSCAT3 (Narita et al. 2020), TESS (Ricker et al. 2015).
Group:Astronomy Department
Funding AgencyGrant Number
Princeton UniversityUNSPECIFIED
Heising-Simons Foundation51 Pegasi b Fellowship
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Science and Technology AgencyJPMJPR1775
Japan Society for the Promotion of Science (JSPS)22000005
Japan Society for the Promotion of Science (JSPS)JP15H02063
Japan Society for the Promotion of Science (JSPS)JP17H04574
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Society for the Promotion of Science (JSPS)JP18H05442
Japan Science and Technology AgencyJPMJPR1775
National Institutes of Natural Sciences of JapanAB031010
Subject Keywords:Exoplanet evolution; Open star clusters; Stellar ages
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet evolution (491); Open star clusters (1160); Stellar ages (1581)
Record Number:CaltechAUTHORS:20220119-234003658
Persistent URL:
Official Citation:L. G. Bouma et al 2022 AJ 163 121
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:113010
Deposited By: George Porter
Deposited On:20 Jan 2022 18:33
Last Modified:15 Feb 2022 18:10

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