In a finding scientists call “an absolute surprise,” a team using NASA’s James Webb Space Telescope has uncovered a rare type of exoplanet whose atmospheric composition challenges current theories of how the planet could have formed. This Jupiter-mass body appears to have an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before.

This exoplanet is orbiting a pulsar, a rapidly spinning neutron star that is the mass of the Sun but the size of a city. The pulsar emits beams of electromagnetic radiation from its magnetic poles at regular intervals of just milliseconds. Together, the star and exoplanet may be considered a “black widow” system, though not a typical example. Black widow systems are a rare type of double system where a pulsar is paired with a small, low-mass stellar companion. Like the spider for which it is named, the pulsar slowly consumes its unfortunate partner. But in this unique case, the companion is an exoplanet, not a star.