Astronomers have identified a planet that pushes well past what current models say should be possible. It’s roughly the size of Jupiter, stretched out of shape by gravity, and orbiting a pulsar, the ultra-dense remnant of a dead star. Its atmosphere is so carbon-heavy that researchers still aren’t sure how it formed at all.
The planet, known as PSR J2322-2650b, completes a full orbit every 7.8 hours. That puts it extremely close to its host pulsar, which bombards the planet with high-energy radiation. Observations suggest atmospheric temperatures reach roughly 3,700 degrees Fahrenheit on the dayside, while the nightside cools to around 1,200 degrees.
The intense gravity and heat distort the planet’s shape, pulling it into an elongated, lemon-like form.
A Lemon-Shaped Planet Is Breaking Everything We Know About Planet Formation
With the James Webb Space Telescope, scientists studied the planet throughout its full orbit to examine how light passed through its atmosphere. They weren’t expecting what they found. Rather than detecting the typical blend of hydrogen, oxygen, and nitrogen common on gas giants, they discovered the spectrum was filled with carbon-based molecules. Signals from carbon chains known as C2 and C3 appeared clearly, while oxygen and nitrogen were scarce or missing.
“The planet orbits a star that’s completely bizarre—the mass of the Sun, but the size of a city,” said Michael Zhang, the study’s lead author, in a statement shared by StudyFinds. “This is a new type of planet atmosphere that nobody has ever seen before.”
The ratios are extreme. The carbon-to-oxygen ratio exceeds 100 to one. Carbon-to-nitrogen climbs above 10,000 to one. No known planet around a normal star comes close to those numbers, and existing theories about how planets form around pulsars don’t explain them either.
Systems like this are often called black widows. Over time, a pulsar strips material from a companion star, sometimes leaving behind a dense remnant. That process should result in a mix of elements, not an atmosphere so heavily skewed toward carbon. The team explored several explanations, including unusual stellar chemistry or carbon-rich dust, but none fully account for what Webb observed.
The planet’s heating also behaves differently from typical hot Jupiters. Gamma rays penetrate deeper into the atmosphere, driving wind patterns that shift heat westward rather than directly away from the pulsar. The hottest region doesn’t sit where models would normally predict.
For now, PSR J2322-2650b stands as a clear outlier. Webb confirmed what’s there. How it came to be remains unresolved.
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