Astrophysics, Relativity, and Cosmology Seminar - Michael Zhang (University of Chicago) "The carbon-rich atmosphere of a windy pulsar planet"
- Event Type
- Seminar/Symposium
- Sponsor
- Department of Physics
- Location
- Rhondale Tso Seminar Room, Loomis 236
- Virtual
- Join online
- Date
- Sep 17, 2025 11:00 am
- Speaker
- Michael Zhang (University of Chicago)
- Contact
- Deanna Frye
- ddebord@illinois.edu
- Views
- 50
A handful of enigmatic Jupiter-mass objects have been discovered orbiting millisecond pulsars. Only one such object, PSR J2322-2650b, resembles a hot Jupiter due to its minimum density of 1.8 g/cm^3 and its ~1900 K temperature. We used JWST to observe its emission spectrum across an entire orbit, finding--in stark contrast to every known exoplanet orbiting a main-sequence star--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 ratio of >100 and C/N ratio of >10,000) 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 low-mass pulsar companions, which were expected to consist of a wider range of elements due to their origins as stripped stellar cores.