DEM L71 presents a textbook example of the double-shock structure expected to develop
when a star explodes and ejects matter at high speeds into the surrounding interstellar gas.
The expanding ejecta drive an outward-moving shock wave that races ahead of the iron-rich ejecta
into the interstellar gas (bright outer rim). The pressure behind this shock wave drives an
inward-moving shock wave that heats the ejecta, seen as the aqua cloud.

The clear separation of the shocked matter and the heated ejecta in the Chandra image
allowed astronomers to determine the mass and composition of the ejecta. The computed
ejected mass was found to be comparable to the mass of the Sun. This and the X-ray
spectrum, which exhibits a high concentration of iron atoms relative to oxygen and silicon,
convincingly show that the ejecta are the remains of an exploded white dwarf star.
The size and temperature of the remnant indicate that it is several thousand years old