Supernova
A supernova is the explosive death of a star, during which it rapidly ejects most of its mass in a brilliant burst of light. In core‑collapse supernovae (Types Ib, Ic, II), massive stars (≥ 8 solar masses) exhaust their nuclear fuel, collapse under gravity, and explode. In Type Ia supernovae, a white dwarf in a binary system undergoes runaway fusion after accreting mass. These events deliver heavy elements into space, leave behind neutron stars or black holes, and power typical shock‑front supernova remnants.
Source: heasarc.gsfc.nasa.gov
APODs including "Supernova"
The Elusive Jellyfish Nebula
09/01/2013
Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic view. Drifting near bright star Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is seen dangling tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 100 light-years across. Best of APOD 2012: Download a free 2013 APOD Calendar