The James Webb Space Telescope NIRSpec-PRISM Transmission Spectrum of the Super-Puff, Kepler-51d
The James Webb Space Telescope NIRSpec-PRISM Transmission Spectrum of the Super-Puff, Kepler-51d
Kepler-51 is a 500 Myr G dwarf hosting three "super-puffs" and one low-mass non-transiting planet. Kepler-51d, the coolest (T_eq ~ 350 K) transiting planet in this system, is also one of the lowest density super-puffs known to date (rho_p = 0.038 +/- 0.009 g/cm^3). With a planetary mass of Mp = 5.6 +/- 1.2 Earth masses and a radius of Rp = 9.32 +/- 0.18 Earth radii, the observed properties of this planet are not readily explained by most planet formation theories. Hypotheses explaining Kepler-51d's low density range from a substantial H/He envelope comprising more than 30% of its mass, to a high-altitude haze layer, to a tilted ring system. To test these hypotheses, we present the NIRSpec-PRISM 0.6-5.3 micron transmission spectrum of Kepler-51d observed by the James Webb Space Telescope. We find a spectrum best fit by a sloped line covering the entire wavelength range. Based on forward modeling and atmosphere retrievals, Kepler-51d likely possesses a low-metallicity atmosphere with high-altitude hazes of submicron particle sizes spanning pressures of 1-100 microbars. However, the spectrum could also be explained by a tilted ring with an estimated lifetime on the order of ~0.1 Myr. We also investigate the stellar activity of this young Sun-like star, extracting a spot temperature significantly hotter than sunspots and spot covering fractions on the order of 0.1-10%, depending on the assumed spot parameters.
Jessica E. Libby-Roberts、Aaron Bello-Arufe、Zachory K. Berta-Thompson、Caleb I. Ca?as、Yayaati Chachan、Renyu Hu、Yui Kawashima、Catriona Murray、Kazumasa Ohno、Armen Tokadjian、Suvrath Mahadevan、Kento Masuda、Leslie Hebb、Caroline Morley、Guangwei Fu、Peter Gao、Kevin B. Stevenson
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Jessica E. Libby-Roberts,Aaron Bello-Arufe,Zachory K. Berta-Thompson,Caleb I. Ca?as,Yayaati Chachan,Renyu Hu,Yui Kawashima,Catriona Murray,Kazumasa Ohno,Armen Tokadjian,Suvrath Mahadevan,Kento Masuda,Leslie Hebb,Caroline Morley,Guangwei Fu,Peter Gao,Kevin B. Stevenson.The James Webb Space Telescope NIRSpec-PRISM Transmission Spectrum of the Super-Puff, Kepler-51d[EB/OL].(2025-05-27)[2025-07-23].https://arxiv.org/abs/2505.21358.点此复制
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