Discovery of an Exterior Third Planet Orbiting β Pictoris

2026/06/22 by Aidan Gibbs, Jean-Baptiste Ruffio, Alexis Bidot +9 · 2 voices
#astro-ph.EP

paper · pdf

Abstract

We report the discovery of β Pictoris d (β Pic d), a third giant planet in the β Pictoris system, which now becomes only the second directly imaged system with more than two confirmed planets. β Pic d was serendipitously detected in JWST/NIRSpec IFU observations. A second epoch of NIRSpec and MIRI/MRS observations confirm the initial discovery. The extracted spectrum shows clear CH₄, CO, and H₂O absorption features, and β Pic d's measured radial velocity is consistent with its orbital position. Radial velocity and astrometry measurements combined with orbital stability simulations suggest a semi-major axis >30 au, consistent with β Pic d being responsible for carving the inner edge of the β Pictoris debris disk. Using effective temperature estimates from atmosphere model grid fits combined with evolutionary models, we estimate a mass of 2--4 M_Jup. β Pic d is the first planet discovered using spectral template matching with moderate-resolution spectroscopy, highlighting its sensitivity to planetary molecular features hidden within bright extrasolar debris disks that are difficult to access with broadband imaging.

Citations

• Jupiter-like uniform metal enrichment in a system of multiple giant exoplanets
• WIde Separation Planets In Time (WISPIT)
• Dynamics of the <i>β</i> Pictoris planetary system and possibility of an additional planet
• The Mid-infrared Instrument for JWST and Its In-flight Performance
• In-orbit Performance of the Near-infrared Spectrograph NIRSpec on the James Webb Space Telescope

Discussions

• Today's arXiv Day: two papers reporting the discovery of Beta Pictoris d. arxiv.org/abs/2606.23789 arxiv.org/abs/2606.23801 #arXiv #arXivDay #exoplanet [bsky, 22 points, 3 comments]
• Direct Imaging Discovery of Giant Exoplanet β Pictoris d - A Decade-Long Game of Hide-and-Seek / Discovery of an Exterior Third Planet Orbiting Pictoris: arxiv.org/abs/2606.23801 / arxiv.org/abs/2606 [bsky, 2 points, 0 comments]

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