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"
A Year of Resolving Backgrounds
30/12/2000
No matter which direction you look, no matter what type of light you see, the sky glows - but why? The sources of many of these background radiations have remained long-standing puzzles, but this millennial year brought some partial resolutions. In X-ray light the recently launched spacecraft Chandra and XMM resolved much of the seemingly uniform X-ray background into many discrete sources, many of which appear to be black holes at the centers of galaxies accreting matter. In microwave light, the BOOMERANG and MAXIMA-1 missions resolved with new clarity the seemingly uniform microwave background. The size and distribution of these spots indicates a geometrically flat universe, which, when combined recent supernovae results, indicate a universe with an accelerating expansion rate filled with dark matter and dark energy. Pictured above, a map spanning ten degrees of the microwave sky resolves the microwave background into hot and cold spots, as indicated in microkelvins.