Stellar Composition May Reveal Origins of Bizarre Planets

The current hypothesis for the formation of Ultra-Short Period Planets, USPs (exoplanets with periods less than 1 day) is that they are remnants of hot Jupiters (gas giants with periods between 1 and 10 days) that experienced tidal decay. Winn et al. (2017) tested this hypothesis by asking whether USPs are associated with metal-rich stars, as has long been observed for hot Jupiters. They gathered stellar metallicity data based on Keck spectroscopy of stars observed by the Kepler mission, then compared the stellar metallicities of USP host stars and hot Jupiter host stars. They concluded that USPs and hot Jupiters are two different types of planets based on their metallicity analysis. We attempted to replicate Winn et al.’s data with a larger sample size to explore how statistically robust their calculations are.