A Preponderance of Perpendicular Planets
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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2021
- DOI:
- 10.3847/2041-8213/ac0f03
- arXiv:
- arXiv:2105.09327
- Bibcode:
- 2021ApJ...916L...1A
- Keywords:
-
- Exoplanet dynamics;
- Exoplanet tides;
- Stellar rotation;
- Exoplanet astronomy;
- Planet hosting stars;
- 490;
- 497;
- 1629;
- 486;
- 1242;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- accepted version, ApJL