Exoplanets, -moons, -comets

A Carbon-rich Atmosphere On A Windy Pulsar Planet

By Keith Cowing
Status Report
astro-ph.EP
September 15, 2025
Filed under , , , , , , ,
A Carbon-rich Atmosphere On A Windy Pulsar Planet
The companion light curve in two continuum bands interpreted with a pulsar direct heating model. (a) The models are shown by the curves and the data are shown by the points. The model does not capture the strong orbit-to-orbit variations at minimum (ϕ ∼ 0 and ϕ ∼ 1), but provides a good description of the flux from the heated face and constrains the binary parameters (see Appendix 5). Schematics of the Earth-view of the heated companion’s surface temperature are shown below the light curve. (b),(c) The residuals of the models compared to their corresponding light curves. astro-ph.EP

A handful of enigmatic Jupiter-mass objects have been discovered orbiting pulsars. One such object, PSR J2322-2650b, uniquely resembles a hot Jupiter exoplanet due to its minimum density of 1.8 g/cm^3 and its ~1900 K equilibrium temperature.

We use JWST to observe its emission spectrum across an entire orbit. In stark contrast to every known exoplanet orbiting a main-sequence star, we find an atmosphere rich in molecular carbon (C3, C2) with strong westward winds.

Our observations open up a new exoplanetary chemical regime (ultra-high C/O and C/N ratios of >100 and >10,000 respectively) and dynamical regime (ultra-fast rotation with external irradiation) to observational study.

The extreme carbon enrichment poses a severe challenge to the current understanding of “black widow” companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores.

Michael Zhang, Maya Beleznay, Timothy D. Brandt, Roger W. Romani, Peter Gao, Hayley Beltz, Matthew Bailes, Matthew C. Nixon, Jacob L. Bean, Thaddeus D. Komacek, Brandon P. Coy, Guangwei Fu, Rafael Luque, Daniel J. Reardon, Emma Carli, Ryan M. Shannon, Jonathan J. Fortney, Anjali A.A. Piette, M. Coleman Miller, Jean-Michel Desert

Comments: Submitted to ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2509.04558 [astro-ph.EP] (or arXiv:2509.04558v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2509.04558
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Submission history
From: Michael Zhang
[v1] Thu, 4 Sep 2025 18:00:00 UTC (3,491 KB)
https://arxiv.org/abs/2509.04558
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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