Spin-orbit angle measurements for six southern transiting planets

TLDR

Hot‑Jupiter formation theories differ, but the orbital obliquity relative to the stellar spin is a more stable diagnostic than other evolving parameters. Most transiting planets are aligned with their host stars, whereas the few misaligned ones are typically massive (>2 MJ).

Abstract

Context. Several competing scenarios for planetary-system formation and evolution seek to explain how hot Jupiters came to be so close to their parent stars. Most planetary parameters evolve with time, making it hard to distinguish between models. The obliquity of an orbit with respect to the stellar rotation axis is thought to be more stable than other parameters such as eccentricity. Most planets, to date, appear aligned with the stellar rotation axis; the few misaligned planets so far detected are massive (> 2MJ).