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Webb Reveals Lemon-Shaped Pulsar Planet With a Carbon-Rich, Helium Atmosphere

JWST spectra expose a chemically exotic companion with no clear origin story as it endures extreme tides next to a neutron star.

Overview

  • The Jupiter-mass world orbits its pulsar at roughly a million miles in a 7.8-hour year, with tidal forces stretching it into a pronounced ellipsoidal shape.
  • Infrared observations detect molecular carbon (C2 and C3) dominating alongside helium, with little to no oxygen or nitrogen evident in the atmosphere.
  • Temperatures span about 1,200°F on the nightside to roughly 3,700°F on the dayside, with analyses indicating soot clouds and conditions that could produce diamond rain.
  • Researchers note the system resembles a black widow scenario in which a pulsar strips its companion, yet no known formation pathway fully explains the measured composition.
  • The results, published December 16 in The Astrophysical Journal Letters, exploit the pulsar’s clean infrared background to deliver an unusually pristine planetary spectrum.