[2607.01316] Aerosols and hydrocarbons in the atmosphere of a white dwarf planet

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Astrophysics > Earth and Planetary Astrophysics

arXiv:2607.01316 (astro-ph)

[Submitted on 1 Jul 2026]

Title:Aerosols and hydrocarbons in the atmosphere of a white dwarf planet

Authors:Ryan J. MacDonald, Christopher E. O'Connor, Victoria A. Boehm, E. M. May, David K. Sing, Elijah Mullens, L. C. Mayorga, Trevor O. Foote, Simon Blouin, Logan A. Pearce, Nikole K. Lewis, Jeff Valenti, Natasha E. Batalha, Maura Lally, Joshua D. Lothringer, Mark S. Marley, Ishan Mishra, Susan E. Mullally<br>View a PDF of the paper titled Aerosols and hydrocarbons in the atmosphere of a white dwarf planet, by Ryan J. MacDonald and 16 other authors

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Abstract:Most stars, including our Sun, will one day evolve into red giants and, subsequently, white dwarfs. Several planet candidates have recently been identified orbiting white dwarfs, demonstrating that planets can survive the stellar post-main-sequence stage intact. Little is known about the atmospheric composition of post-main-sequence planets, with the most evolved transiting planets with atmospheric detections to date orbiting subgiants. Here we report an atmospheric detection for the white dwarf planet WD 1856 b, achieved through transmission spectroscopy with the JWST NIRSpec PRISM. Our 0.5-5.0 $\mu$m spectrum reveals the presence of hydrocarbons (odds ratio of $167:1$ to $5377:1$, with $\mathrm{CH}_4$ preferred at $17:1$ to $30:1$), aerosols ($2 \times 10^5:1$ to $2 \times 10^6:1$), and thermal emission from the planetary nightside ($2 \times 10^{63}:1$ to $2 \times 10^{73}:1$). Our spectral analysis constrains WD 1856 b's mass to $4.3$ to $10.9 \mathrm{M}_J$, finds a carbon-enriched atmosphere (with a $\mathrm{CH}_4$ abundance of $\approx 7\%$), and an effective temperature exceeding the expected planetary equilibrium temperature ($390$ to $412 \, \mathrm{K}$ vs. $160 \, \mathrm{K}$). Based on cooling models, these results suggest that WD 1856 b underwent a migration-related reheating event $3.0$ to $5.5 \, \mathrm{Gyr}$ into the white dwarf phase, consistent with post-main-sequence tidal evolution to the present-day $0.02 \, \mathrm{au}$ circular orbit. Our results provide a window into the ultimate fate of giant planets orbiting stars with masses similar to our Sun.

Comments:<br>28 pages, 12 figures, 3 tables. Published in Nature (1 July 2026). Accepted manuscript, for the version of record see: this https URL

Subjects:

Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Cite as:<br>arXiv:2607.01316 [astro-ph.EP]

(or<br>arXiv:2607.01316v1 [astro-ph.EP] for this version)

https://doi.org/10.48550/arXiv.2607.01316

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arXiv-issued DOI via DataCite

Journal reference:<br>Nature 655, 76-80 (2026)

Related DOI:

https://doi.org/10.1038/s41586-026-10514-7

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DOI(s) linking to related resources

Submission history<br>From: Ryan MacDonald [view email]<br>[v1]<br>Wed, 1 Jul 2026 18:00:00 UTC (12,046 KB)

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