Space is full of unsolved mysteries, and a team using NASA’s James Webb Space Telescope have recently turned up a doozy. “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,” said Peter Gao of the Carnegie Earth and Planets Laboratory in Washington, a co-author on the study.

The researchers found an exoplanet dubbed PSR J2322-2650b that orbits a small, dense star emitting electromagnetic radiation known as a pulsar. They are an example of a black widow system, where a rapidly spinning pulsar is paired with a smaller astronomical body. A black widow duo isn’t unusual, but this pair has sparked questions about how the exoplanet originally formed.

The exoplanet’s proximity to the pulsar and its intense gravitational pull have distorted it into an oblong lemon shape. More unusually, PSR J2322-2650b also has a unique atmosphere comprised mostly of helium and carbon. “Instead of finding the normal molecules we expect to see on an exoplanet — like water, methane, and carbon dioxide — we saw molecular carbon,” principal investigator Michael Zhang of University of Chicago said. Given its strange atmosphere, the team isn’t certain how the exoplanet formed. “It’s very hard to imagine how you get this extremely carbon-enriched composition. It seems to rule out every known formation mechanism,” Zhang said. For now, we’ll chalk this up as another mystery of the universe.