The bizarre, grinch-like wisp of green light dubbed the Green Monster, first seen last year snaking through the glowing remnants of an exploded star, belongs to a blast wave bordering the debris field, a new study reveals.
Last April, NASA's James Webb Space Telescope (JWST or Webb) photographed the unusual "wall of emission" in front of Cassiopeia A (or Cas A), an expanding shell of hot gas roughly 11,000 light-years from Earth whose light first reached us 340 years ago. For the past year, astronomers have been trying to explain its origin and presence in the well-studied supernova remnant.
