The Featherweight Giant: Unraveling the Atmosphere of a 17 Myr Planet with JWST
Pa Chia Thao, Andrew W. Mann, Adina D. Feinstein, Peter Gao, Daniel, Thorngren, Yoav Rotman, Luis Welbanks, Alexander Brown, Girish M. Duvvuri,, Kevin France, Isabella Longo, Angeli Sandoval, P. Christian Schneider, David, J. Wilson, Allison Youngblood, Andrew Vanderburg

TL;DR
This study presents the first detailed atmospheric characterization of a young, 17-million-year-old planet, HIP 67522 b, revealing its low density, composition, and evolutionary state using JWST data, challenging previous classifications.
Contribution
It provides the first transmission spectrum of a young planet with JWST, constrains its mass and composition, and offers insights into early planetary evolution and atmospheric properties.
Findings
HIP 67522 b has a mass of approximately 13.8 M_⊕.
The planet exhibits strong H2O and CO2 absorption features.
It is likely experiencing significant atmospheric mass loss.
Abstract
The characterization of young planets (< 300 Myr) is pivotal for understanding planet formation and evolution. We present the 3-5m transmission spectrum of the 17 Myr, Jupiter-size ( 10) planet, HIP 67522 b, observed with JWST/NIRSpec/G395H. To check for spot contamination, we obtain a simultaneous -band transit with SOAR. The spectrum exhibits absorption features 30-50% deeper than the overall depth, far larger than expected from an equivalent mature planet, and suggests that HIP 67522 b's mass is 20 irrespective of cloud cover and stellar contamination. A Bayesian retrieval analysis returns a mass constraint of . This challenges the previous classification of HIP 67522 b as a hot Jupiter and instead, positions it as a precursor to the more common sub-Neptunes. With a density of 0.10g/cm, HIP 67522 b is one of…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
Taxonomy
TopicsStellar, planetary, and galactic studies · Astronomy and Astrophysical Research · Gamma-ray bursts and supernovae
