The James Webb Space Telescope has observed a Jupiter-sized companion orbiting pulsar J2322‑2650 whose atmosphere is dominated by helium and an exceptionally high abundance of molecular carbon, along with strong westerly winds. Tidally locked and stretched into an elongated shape, the companion’s dayside is continually bombarded by gamma rays while the far side remains dark. Standard formation scenarios — including black widow stripping and white-dwarf mergers — do not yet explain the extreme carbon dominance. The object’s current properties are constrained, but its origin remains an unsolved mystery.
JWST Reveals Carbon-Rich, Jupiter-Sized Companion Orbiting Pulsar J2322‑2650
An artist's conception of the pulsar's companion. Photo: NASA/JWST/ESA/CSA/Ralf Crawford (STScI)
Astronomers using the James Webb Space Telescope have observed an extraordinary Jupiter-sized object orbiting the energetic pulsar J2322‑2650. The companion’s atmosphere is dominated by helium and an unusually high concentration of molecular carbon, and JWST data show powerful westerly winds sweeping across its surface.
How This Strange System Was Found
The companion was identified not by traditional exoplanet searches but through tiny variations in the pulsar’s radio pulse timings. Pulsars are rapidly spinning neutron stars that emit extremely regular radio pulses; careful timing of those pulses can reveal the gravitational tug of orbiting bodies. That led astronomers to point JWST at J2322‑2650 and capture the unusual spectrum of its faint, Jupiter-sized companion.
A composite optical and X-ray image of the original black widow pulsar. The extended pink blob shows the shocked gas around the pulsar. Photo: By X-ray: NASA/CXC/ASTRON/B.Stappers et al.; Optical: AAO/J.Bland-Hawthorn & H.Jones
An Atmosphere Like Nothing Else
Most gas giants are dominated by hydrogen, often with helium and trace molecules such as methane or ammonia. By contrast, the JWST spectra indicate an atmosphere composed mainly of helium plus an extraordinary abundance of molecular carbon in gaseous form. This is not the typical mix of hydrocarbons seen in space; instead the data suggest a very carbon-dominated chemistry — something with no close analogue in the Solar System, where pure carbon normally appears as solid graphite or diamond.
"What the heck is this?" co-author Peter Gao recalled the team saying when they first inspected the spectra. "It's extremely different from what we expected."
Tidally Locked, Stretched, and Bombarded
The companion lies so close to the pulsar that tidal forces keep one hemisphere facing the neutron star at all times, a state known as tidal locking. That asymmetry stretches the object into an elongated, lemon- or football-like shape and produces a permanent dayside exposed to intense gamma-ray and X-ray irradiation while the far side remains in darkness. The irradiation and extreme temperature contrasts likely drive the strong westerly winds detected by JWST.
Formation Mysteries
Could this be the remnant of a classic "black widow" pulsar — a system where the pulsar slowly strips away a companion’s atmosphere? Typically, black widow companions retain hydrogen signatures, which are absent here. The authors consider more exotic origins, including mergers involving white dwarfs (for example, a helium white dwarf merging with a carbon–oxygen white dwarf), but none of the scenarios yet explain the extreme carbon dominance and relative lack of oxygen. In short: we can describe its present state, but its history remains an open puzzle.
Why it matters: This system challenges our understanding of how extreme irradiation, tidal physics, and prior stellar evolution shape companion bodies. It also demonstrates how pulsar timing plus JWST spectroscopy can uncover unusual objects that standard surveys miss.
Image credit: NASA/JWST/ESA/CSA/Ralf Crawford (STScI).
