NASA’s Webb spots bizarre carbon-rich exoplanet orbiting a rapidly spinning pulsar

A planet that shouldn t exist is rewriting what scientists thought they knew about worlds beyond our solar system. Using NASA s James Webb Space Telescope, researchers have spotted an exoplanet with an atmosphere unlike anything previously observed, one so strange it blurs the line between planet and star.

Officially named PSR J2322-2650b, the object is roughly the mass of Jupiter but bears little resemblance to a typical gas giant. It orbits a rapidly spinning neutron star, or pulsar, at an extremely close distance, enduring intense radiation and gravitational forces that stretch it into a lemon-like shape.

What truly stunned scientists, however, was its atmosphere. Instead of familiar compounds such as water vapor or methane, Webb detected a mix dominated by helium and carbon, an exotic chemistry never before seen on a planet.

The planet orbits a star that s completely bizarre, the mass of the Sun, but the size of a city, said University of Chicago s Michael Zhang, the study s principal investigator. This is a new type of planet atmosphere that nobody has ever seen before. This was an absolute surprise, added team member Peter Gao of the Carnegie Earth and Planets Laboratory. I remember after we got the data down, our collective reaction was What the heck is this?' A planet without starlight PSR J2322-2650b circles its pulsar at a distance of just about one million miles, completing a full orbit every 7.8 hours.

The host star emits mostly gamma rays and high-energy particles, which are invisible to Webb s infrared instruments. That unusual setup gave scientists a rare advantage. With the pulsar effectively invisible, the planet s faint glow could be studied in remarkable detail. This system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all, said Stanford University graduate student Maya Beleznay.

So we get a really pristine spectrum. The data revealed molecular carbon, specifically C₂ and C₃, floating through the planet s atmosphere, along with soot-like clouds.

Deep inside, under extreme pressure, that carbon could even condense into diamonds. Instead of finding the normal molecules we expect to see on an exoplanet, like water, methane, and carbon dioxide, we saw molecular carbon, specifically C3 and C2, Zhang said.

Formation theories fall apart The discovery raises a bigger question: how did such a planet form at all? It s very hard to imagine how you get this extremely carbon-enriched composition, Zhang said. It seems to rule out every known formation mechanism. The system resembles a rare black widow pairing, where a pulsar slowly strips material from a smaller companion.

But even that explanation falls short. Did this thing form like a normal planet? No, because the composition is entirely different, Zhang said. Did it form by stripping the outside of a star, like normal black widow systems are formed?

Probably not, because nuclear physics does not make pure carbon. Roger Romani of Stanford University suggests an unusual process may be at work. Pure carbon crystals float to the top and get mixed into the helium, he said. But then something has to happen to keep the oxygen and nitrogen away.

For now, the planet remains a cosmic puzzle. The study appears in the journal The Astrophysical Journal Letters.