Cassiopeia A

supernova remnant · the youngest known from a massive star

11,000 light-years from Earth

The shredded remains of a massive star whose light from the explosion reached Earth around the 1660s, though nobody is known to have seen it. JWST sees its debris as knots of orange and pink, a shock front ahead of it, and a curious green curtain nicknamed the Green Monster.

• 11,000 light-years · about 10 light-years across
• its debris still flies outward at up to 14,000 km/s

kind

nebula · explosion or collision