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

Kepler 1627A is a G8V star previously known to host a 3.8 R-circle plus 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(-5)(+6) Myr old delta 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 delta Lyr cluster is one of similar to 10(3) 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.

Automated summary

Kepler 1627A is a member of the delta Lyr cluster and hosts the youngest planet, Kepler 1627Ab. The Kepler photometry shows peculiarities, possibly correlated with the planet's characteristics.