2021/05/31 by Simon Albrecht, Simon H. Albrecht, Marcus L. Marcussen +3 · 102 citations
Mathematics · Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Geodesy #Geology #Geometry #Lambda #Line (geometry) #Line-of-sight #Mathematics #Optics #Perpendicular #Physics #Planet #Population #Sky #Span (engineering) #Spin (aerodynamics) #Stellar, planetary, and galactic studies #astro-ph.EP #astro-ph.SR
paper · pdf · doi:10.3847/2041-8213/ac0f03
published in The Astrophysical Journal Letters 916(1), L1 (IOP Publishing) · accepted version, ApJL
arxiv created 2021/06/28 · openalex publication_date 2021/07/01 · arxiv updated 2021/10/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract Observing the Rossiter–McLaughlin effect during a planetary transit allows the determination of the angle λ between the sky projections of the star’s spin axis and the planet’s orbital axis. Such observations have revealed a large population of well-aligned systems and a smaller population of misaligned systems, with values of λ ranging up to 180°. For a subset of 57 systems, we can now go beyond the sky projection and determine the 3D obliquity ψ by combining the Rossiter–McLaughlin data with constraints on the line-of-sight inclination of the spin axis. Here we show that the misaligned systems do not span the full range of obliquities; they show a preference for nearly perpendicular orbits ( ψ = 80°–125°) that seems unlikely to be a statistical fluke. If confirmed by further observations, this pile-up of polar orbits is a clue about the unknown processes of obliquity excitation and evolution.