A Carbon-rich Atmosphere on a Windy Pulsar Planet

Journal article

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 PSR J2322–2650b’s 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 new exoplanetary chemical (ultrahigh C/O and C/N ratios of >100 and >10,000, respectively) and dynamical regimes (ultrafast 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.

Authors: Zhang, M; Beleznay, M; Brandt, TD; Romani, RW; Gao, P

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Astronomical Society
• Journal: The Astrophysical Journal Letters
• Volume: 995
• Issue: 2
• Article number: L64
• Publication date: 2025-12-16
• Acceptance date: 2025-10-08
• DOI: 10.3847/2041-8213/ae157c
• EISSN: 2041-8213
• ISSN: 2041-8205
• Language: English
• Keywords: Carbon planets; Pulsar planets; Hot Jupiters; Stellar atmospheres; High energy astrophysics