New details from NASA's James Webb Space Telescope refine our view of PSR J2322-2650b, the carbon-rich, lemon-shaped exoplanet orbiting a pulsar just 1 million miles away. Building on initial reports, its helium-carbon atmosphere harbors C2 and C3 molecules, soot clouds, and possible diamond crystals under extreme pressure, as detailed in The Astrophysical Journal Letters.
Initial observations of PSR J2322-2650b, a Jupiter-mass exoplanet over 2000 light-years away, revealed its bizarre carbon-dominated atmosphere lacking typical water or methane. Further spectroscopy confirms a helium- and carbon-rich composition with C3 and C2 molecules, dark soot-like clouds of graphite, and carbon potentially crystallizing into diamonds deep inside due to immense pressures.
Orbiting a city-sized pulsar with the Sun's mass every 7.8 hours, the planet endures tidal forces distorting it into a lemon shape. Temperatures exceed 650°C even at 'cold' spots, with retrograde winds. "The planet orbits a star that's completely bizarre," said lead investigator Michael Zhang of the University of Chicago. "Instead of finding normal molecules... we saw molecular carbon."
The pulsar's emissions do not affect Webb's infrared views, enabling orbit-wide spectra. Stanford grad student Maya Beleznay modeled its oblate path and shape: "We are able to view the planet illuminated by its host star, but not see the host star at all."
This may be a black widow system, where the pulsar erodes its companion. Formation puzzles persist: "It's very hard to imagine how you get this extremely carbon-enriched composition," Zhang noted. Carnegie’s Peter Gao called it an "absolute surprise," while Stanford’s Roger Romani suggested rising carbon crystals during cooling.
Zhang described it as a "deep red" world with graphite clouds, "like a sort of evil lemon"—the weirdest exoplanet yet. Findings, funded by NASA and the Heising-Simons Foundation, involve Jacob Bean and others from the University of Chicago (DOI: 10.3847/2041-8213/ae157c).
