White Dwarf
The dense, hot core left behind after a low- or intermediate-mass star expels its outer layers. White dwarfs are composed mostly of electron-degenerate matter and no longer undergo fusion.
Source: chandra.harvard.edu
APODs including "White Dwarf"
The X-ray Timing Explorer
03/01/1996
Launched Saturday on a Delta rocket, the X-ray Timing Explorer (XTE) will watch the sky for rapid changes in X-rays. XTE carries three separate X-ray telescopes. The Proportional Counter Array (PCA) and the High Energy X-ray Timing Experiment (HEXTE) will provide the best timing information in the widest X-ray energy range yet available. They will observe stellar systems that contain black holes, neutron stars, and white dwarfs as well as study the X-ray properties of the centers of active galaxies. XTE's All Sky Monitor (ASM) will scan the sky every 90 minutes to find new X-ray transients and track the variability of old ones. XTE has a planned life time of two years.