🪐 First direct image of a planet so close to binary stars

An international research team announces the discovery of a new exoplanet orbiting a binary star system. Named HD 143811 b, this giant planet joins the very exclusive club of exoplanets detected by direct imaging using the SPHERE instruments on the Very Large Telescope (VLT) and the GPI on the Gemini South telescope - a first for these two joint instruments and only the second planet ever discovered by GPI.

Understanding planet formation sheds light on the birth of our solar system and our own origins. Unlike the Sun, the sole star in our solar system, most stars are born in pairs or groups within multiple systems. Therefore, estimating the effect of this binarity on planet formation is crucial. Yet, detections of planets in these systems - sometimes nicknamed Tatooine-type planets, in reference to Star Wars - remain exceptionally rare.


This is particularly true for those whose light can be photographed directly, a technique that allows for the analysis of their atmospheric composition. To date, only six circumbinary planets had been detected by direct imaging, a sample far too small to understand their formation mechanisms compared to single-star systems.

This discovery is the result of the ERC COBREX project, which systematically reanalyzes thousands of archive observations with advanced tools that significantly improve planet detection. By revisiting data from the Gemini Planet Imager, the team identified candidates that had been missed in initial analyses. One of them was orbiting HD 143811, a young binary system (15 million years old) located 137 parsecs (447 light-years) away in the Scorpius-Centaurus association, the closest stellar nursery to us.

Observed in 2016 and 2019 with GPI, this candidate appeared to follow the stars in their motion, but its faint signal in 2019 left room for doubt. A new observation with SPHERE in July 2025 was decisive: the companion was shining exactly at the expected position for an orbiting planet. Thanks to this effort, the team confirmed HD 143811 b, which joins the small group of about 50 planets directly photographed over the past 20 years.

HD 143811 b is remarkable for several reasons. It becomes the seventh circumbinary planet ever imaged and, most importantly, the closest to its stars: it orbits at only 60 astronomical units, a distance approaching that of our solar system, whereas other known circumbinary planets are typically found hundreds of astronomical units away. It is also one of the least massive in this category. Due to its proximity and moderate mass, it constitutes a unique benchmark for studying planet formation in binary systems.

The nine years of observations allowed the reconstruction of its orbit: it revolves around its two suns in about 320 years on a nearly circular trajectory, viewed almost face-on from Earth. Analysis of its light revealed a surface temperature of 1000 Kelvin, corresponding to a gaseous planet 6.1 times more massive than Jupiter, but only 40% wider. The planet still appears hot and inflated, like all gas giants in their youth.

In the coming months, the GRAVITY instruments on the VLT and MIRI on the James Webb Space Telescope will allow for refining its orbit and characterizing in detail the composition of its atmosphere. This discovery also illustrates the potential of reanalyzing archives with modern algorithms. The precise characterization of this new circumbinary planet and the comparison with other young planets will be crucial for understanding the formation mechanisms of these fascinating worlds.