WIde Separation Planets In Time (WISPIT): Two directly imaged exoplanets around the Sun-like stellar binary WISPIT 1

TL;DR

The paper reports the discovery of two gas giant exoplanets at wide separations around a Sun-like binary star, using a dedicated survey that combines imaging and proper motion analysis to identify and characterize these planets.

Contribution

First detection of wide separation gas giant planets around a Sun-like binary star using a systematic imaging survey and proper motion analysis.

Findings

Discovered two co-moving gas giant exoplanets at 338 au and 840 au.

Determined planetary masses of 10 and 4 Jupiter masses.

Identified the host system as a binary with a K4 and M5.5 star.

Abstract

Wide separation gas giant planets present a challenge to current planet formation theories, and the detection and characterisation of these systems enables us to constrain their formation pathways. The WIde Separation Planets In Time (WISPIT) survey aims to detect and characterise wide separation planetary-mass companions over a range of ages from <5 to 20 Myr around solar-type host stars at distances of 75-500 (median: 140) parsecs. The WISPIT survey carries out two 5 minute H-band exposures with the VLT/SPHERE instrument and IRDIS camera, separated by at least six months to identify co-moving companions via proper motion analysis. These two H-band observations in combination with a follow-up Ks-band observation were used to determine the colour-magnitude of the co-moving companions and to derive their masses by comparing to AMES-COND and AMES-DUSTY evolutionary tracks. We report the discovery of WISPIT 1b and WISPIT 1c, two gas giant exoplanets that are co-moving with the stellar binary WISPIT 1, which itself consists of a K4 star and M5.5 star in a multi-decadal orbit. The planets are at projected separations of 338 au and 840 au and have masses of 10 Mj and 4 Mj respectively. We identified two common proper motion planetary companions to a (previously unknown) stellar binary with a Sun-like primary. These targets are ideal for follow up characterisation with both ground and space-based telescopes. Monitoring of the orbit with the GRAVITY interferometer will place constraints on their eccentricity, and spectroscopic characterisation will identify the composition and metallicity, providing information on their formation pathways.