The obliquity of HIP 67522 b: a 17 Myr old transiting hot Jupiter-sized planet

TL;DR

This study measures the orbital obliquity of the 17-million-year-old transiting hot Jupiter HIP 67522 b, revealing a well-aligned orbit that informs theories of planet formation and migration in young planetary systems.

Contribution

First measurement of the obliquity of a very young (17 Myr) hot Jupiter, demonstrating the feasibility of such observations for active young stars.

Findings

System's obliquity is close to zero degrees, indicating a well-aligned orbit.

The system's low obliquity suggests a migration history not dominated by high eccentricity processes.

HIP 67522 b is the youngest planet with a known obliquity, providing new insights into early planetary evolution.

Abstract

HIP 67522 b is a 17 Myr old, close-in ($P_{orb} = 6.96$ d), Jupiter-sized ($R = 10\,R_{\oplus}$) transiting planet orbiting a Sun like star in the Sco-Cen OB association. We present our measurement of the system's projected orbital obliquity via two spectroscopic transit observations using the CHIRON spectroscopic facility. We present a global model that accounts for large surface brightness features typical of such young stars during spectroscopic transit observations. With a value of $|\lambda| = 5.8^{+2.8\,\circ}_{-5.7}$, it is unlikely that this well-aligned system is the result of a high eccentricity driven migration history. By being the youngest planet with a known obliquity, HIP 67522 b holds a special place in contributing to our understanding of giant planet formation and evolution. Our analysis shows the feasibility of such measurements for young and very active stars.