A 16 Hour Transit of Kepler-167 e Observed by the Ground-based Unistellar Telescope Network

TL;DR

This paper reports the ground-based detection of a 16-hour transit of the long-period exoplanet Kepler-167 e using a global telescope network, demonstrating the potential of citizen science and small telescopes for studying distant planets.

Contribution

First ground-based detection of a long-period exoplanet transit using a coordinated network of small telescopes, refining orbital parameters without space telescopes.

Findings

Detected the longest-period planet transit from the ground.

Refined the orbital timing of Kepler-167 e.

Showcased the effectiveness of citizen science networks.

Abstract

More than 5,000 exoplanets have been confirmed and among them almost 4,000 were discovered by the transit method. However, few transiting exoplanets have an orbital period greater than 100 days. Here we report a transit detection of Kepler-167 e, a "Jupiter analog" exoplanet orbiting a K4 star with a period of 1,071 days, using the Unistellar ground-based telescope network. From 2021 November 18 to 20, citizen astronomers located in nine different countries gathered 43 observations, covering the 16 hour long transit. Using a nested sampling approach to combine and fit the observations, we detected the mid-transit time to be UTC 2021 November 19 17:20:51 with a 1$\sigma$ uncertainty of 9.8 minutes, making it the longest-period planet to ever have its transit detected from the ground. This is the fourth transit detection of Kepler-167 e, but the first made from the ground. This timing measurement refines the orbit and keeps the ephemeris up to date without requiring space telescopes. Observations like this demonstrate the capabilities of coordinated networks of small telescopes to identify and characterize planets with long orbital periods.