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6d ago

Webb Finds Carbon-Rich, Helium-Dominated Atmosphere on Pulsar-Orbiting Planet

Because the pulsar emits little infrared light, Webb could read the companion’s atmosphere directly.

Artist's illustration of a strange planet (left) orbits a rapidly spinning neutron star called a pulsar (right).
This artist’s concept shows what PSR J2322-2650b may look like. Image credit: NASA / ESA / CSA / Ralf Crawford, STScI.

Overview

  • JWST spectra reveal a helium-and-carbon-dominated atmosphere with molecular carbon C2 and C3, a composition not seen in prior exoplanet atmospheres.
  • The companion, roughly Jupiter-mass, circles its pulsar in 7.8 hours at about 1 million miles and is tidally stretched into a lemon-like shape.
  • Temperatures range from about 1,200 to 3,700 degrees Fahrenheit, with models suggesting soot clouds and carbon condensing into diamonds deep inside.
  • The host neutron star emits mainly high-energy radiation invisible to Webb, enabling an unusually pristine infrared spectrum across the planet’s orbit.
  • Authors report the findings in The Astrophysical Journal Letters and say known formation pathways appear inadequate, noting a crystallization-and-mixing hypothesis under consideration.