2018/03/31 by Joshua N. Winn, Roberto Sanchis-Ojeda, Saul Rappaport · 2 citations
Physics and Astronomy · #astro-ph.EP
paper · pdf · doi:10.1016/j.newar.2019.03.006
published as New Astronomy Reviews 83 (2018) 37-48 · fixed error in Eq. (4)
arxiv created 2020/02/15 · arxiv updated 2020/02/18
Compared to the Earth, the exoplanet Kepler-78b has a similar size (1.2 R_⊕) and an orbital period a thousand times shorter (8.5 hours). It is currently the smallest planet for which the mass, radius, and dayside brightness have all been measured. Kepler-78b is an exemplar of the ultra-short-period (USP) planets, a category defined by the simple criterion P\rm orb < 1 day. We describe our Fourier-based search of the Kepler data that led to the discovery of Kepler-78b, and review what has since been learned about the population of USP planets. They are about as common as hot Jupiters, and they are almost always smaller than 2 R_⊕. They are often members of compact multi-planet systems, although they tend to have relatively large period ratios and mutual inclinations. They might be the exposed rocky cores of "gas dwarfs," the planets between 2-4 R_⊕ in size that are commonly found in somewhat wider orbits.