Evidence for a sub-Jovian planet in the young TWA 7 disk.

Lagrange, A-M; Wilkinson, C; Mâlin, M; Boccaletti, A; Perrot, C; Matrà, L; Combes, F; Beust, H et al. · Nature · 2025

basic_science · Level V

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Abstract

Planets are thought to form from dust and gas in protoplanetary disks, with debris disks being the remnants of planet formation. Aged a few million up to a few billion years, debris disks have lost their primordial gas, and their dust is produced by steady-state collisions between larger, rocky bodies<sup>1,2</sup>. Tens of debris disks, with sizes of tens, sometimes hundreds, of astronomical units have been resolved with high-spatial-resolution, high-contrast imagers at optical and near-infrared or (sub)millimetre interferometers<sup>3,4</sup>. They commonly show cavities, ring-like structures and gaps, which are often regarded as indirect signatures of the presence of planets that gravitationally interact with unseen planetesimals<sup>2,5</sup>. However, no planet responsible for these features has been detected yet, probably because of the limited sensitivity (typically 2-10 M<sub>J</sub>) of high-contrast imaging instruments (see, for example, refs. <sup>6-9</sup>) before the James Webb Space Telescope. Here we have used the unprecedented sensitivity of the James Webb Space Telescope's Mid-Infrared Instrument<sup>10,11</sup> in the thermal infrared to search for such planets in the disk of the approximately 6.4-Myr-old star TWA 7. With its pole-on orientation, this three-ring debris disk is indeed ideally suited for such a detection. We unambiguously detected a source 1.5 arcsec from the star, which is best interpreted as a cold, sub-Jupiter-mass planet. Its estimated mass (about 0.3 M<sub>J</sub>) and position (about 52 AU, de-projected) can thoroughly account for the main disk structures.