Two Directly Imaged, Wide-orbit Giant Planets around the Young, Solar Analog TYC 8998-760-1

TL;DR

This paper reports the discovery of a second giant planet around the young solar-like star TYC 8998-760-1, making it the first known directly imaged multiplanet system around such a star, with implications for planetary formation theories.

Contribution

It presents the first directly imaged multiplanet system around a young, solar analog, with detailed characterization of the companions and analysis of their orbital stability.

Findings

Discovered a second planetary-mass companion at 320 au

Confirmed the first companion at 160 au, forming a multiplanet system

Analyzed orbital stability, suggesting in-situ formation or specific ejection scenarios.

Abstract

Even though tens of directly imaged companions have been discovered in the past decades, the number of directly confirmed multiplanet systems is still small. Dynamical analysis of these systems imposes important constraints on formation mechanisms of these wide-orbit companions. As part of the Young Suns Exoplanet Survey (YSES) we report the detection of a second planetary-mass companion around the 17 Myr-old, solar-type star TYC 8998-760-1 that is located in the Lower Centaurus Crux subgroup of the Scorpius-Centaurus association. The companion has a projected physical separation of 320 au and several individual photometric measurements from 1.1 to 3.8 microns constrain a companion mass of $6\pm1\,M_\mathrm{Jup}$, which is equivalent to a mass ratio of $q=0.57\pm0.10\%$ with respect to the primary. With the previously detected $14\pm3\,M_\mathrm{Jup}$ companion that is orbiting the primary at 160 au, TYC 8998-760-1 is the first directly imaged multiplanet system that is detected around a young, solar analog. We show that circular orbits are stable, but that mildly eccentric orbits for either/both components ($e > 0.1$) are chaotic on Gyr timescales, implying in-situ formation or a very specific ejection by an unseen third companion. Due to the wide separations of the companions TYC 8998-760-1 is an excellent system for spectroscopic and photometric follow-up with space-based observatories such as the James Webb Space Telescope.