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Webb Finds Helium–Carbon Atmosphere on First Hot Jupiter Known Around a Pulsar

An unusually clean infrared spectrum revealing C2 and C3 leaves the planet’s origin unresolved.

Overview

  • JWST’s NIRSpec captured a pristine day-side spectrum of PSR J2322-2650b dominated by helium with distinct molecular carbon signatures C2 and C3.
  • The gas giant is about 0.8 times Jupiter’s mass with low density and day-side temperatures near 2,040°C.
  • At roughly 1.6 million kilometers from a millisecond pulsar, it completes an orbit in 7.8 hours and is tidally elongated into a lemon-like shape.
  • No established formation pathway accounts for the extreme carbon enrichment with very little oxygen or nitrogen, prompting new hypotheses and planned follow-up searches.
  • Researchers suggest soot clouds may form aloft and that carbon could crystallize into diamonds deeper within the planet, a scenario that remains unconfirmed.