# GPI+SPHERE detection of a 6.1MJup circumbinary planet around HD 143811

**Authors:** Vito Squicciarini, Johan Mazoyer, Christian Wilkinson, Anne-Marie Lagrange, Philippe Delorme, Alice Radcliffe, Olivier Flasseur, Flavien Kiefer, Evelyne Alecian  
**arXiv:** [2509.06009](https://arxiv.org/abs/2509.06009)  
**Date:** 2025-09-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2509.06009v1/

## Key points

- Discovery of exoplanet HD 143811(AB)b orbiting young binary star HD 143811
- COBREX project used advanced post-processing techniques on archival observations from SPHERE and GPI for enhanced detection sensitivity
- Exoplanet located at a projected separation of approximately 60 astronomical units from host star
- Second exoplanet discovered by GPI, part of exclusive group of circumbinary planets detected through direct imaging
- Characterization of atmosphere reveals temperature around 1000 Kelvin and estimated mass of approximately 6.1 Jupiter masses
- Provides valuable insights into intrinsic properties and presents opportunities for further studies on planetary formation in multiple star systems

## Summary

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The discovery of the exoplanet HD 143811(AB)b, orbiting the young binary star HD 143811, represents a significant advancement in our understanding of planet formation and the complex interactions between proto-planetary disks and stellar hosts. The COBREX project utilized advanced post-processing techniques on archival observations from SPHERE and GPI to enhance detection sensitivity at close separations, successfully identifying this new exoplanet candidate. Extensive follow-up observations with SPHERE@VLT confirmed that HD 143811(AB)b is located at a projected separation of approximately 60 astronomical units from its host star. With a mostly face-on and low eccentricity orbit estimated to have a period of around 320 years based on a nine-year baseline, this exoplanet is only the second ever discovered by GPI and joins the exclusive group of circumbinary planets detected through direct imaging. The characterization of HD 143811(AB)b's atmosphere has provided valuable insights into its intrinsic properties. Analysis of H-band spectrum from GPI, H-band photometry from SPHERE/IRDIS, and YJ upper limits from SPHERE/IFS have allowed researchers to constrain the planet's temperature to be around 1000 Kelvin, corresponding to an estimated mass of approximately 6.1 Jupiter masses. This groundbreaking discovery not only adds to our growing knowledge of planetary systems but also presents an exciting opportunity for further studies on formation mechanisms, dynamical behavior, and detailed characterization of circumbinary planets. HD 143811(AB)b stands as a prime target for future research efforts aimed at unraveling the mysteries surrounding planetary formation in multiple star systems.