Astronomers using NASA’s James Webb Space Telescope identified exoplanet PSR J2322-2650b orbiting a small, dense pulsar through spectroscopic analysis. This black widow system features the planet deformed into an oblong lemon shape by the pulsar’s proximity and gravity.
The research team collected data revealing the exoplanet’s unusual characteristics. Peter Gao of the Carnegie Earth and Planets Laboratory in Washington, a co-author on the study, described the initial response: “I remember after we got the data down, our collective reaction was ‘What the heck is this?’ It’s extremely different from what we expected.” The pulsar emits electromagnetic radiation and spins rapidly, paired with the smaller exoplanet in a configuration typical of black widow systems, though this instance raises questions about the planet’s formation.
PSR J2322-2650b maintains an extremely close orbit to the pulsar. The intense gravitational pull from the pulsar distorts the exoplanet’s structure, elongating it into a lemon-like oblong form. This deformation results directly from the gravitational tidal forces exerted due to their tight proximity.
Spectroscopic observations detected an atmosphere composed mainly of helium and carbon. Principal investigator Michael Zhang of the University of Chicago noted the anomaly: “Instead of finding the normal molecules we expect to see on an exoplanet — like water, methane, and carbon dioxide — we saw molecular carbon.” This carbon-rich layer, dominated by molecular carbon alongside helium, deviates from standard exoplanet atmospheres.
The composition poses challenges to understanding the exoplanet’s origins. Zhang explained: “It’s very hard to imagine how you get this extremely carbon-enriched composition. It seems to rule out every known formation mechanism.” The helium-carbon atmosphere lacks alignment with established planetary formation processes observed elsewhere.
