The nebula is now about 7 light years across and 944 years old. Due to differences in image scales, the pictures don't map precisely onto each other. The finely detailed structure, and the dynamic physics, make the Crab one of the most studied objects in the heavens. Of interest here is the thermal evolution of the stars. The physical activity in the star's superfluid interior, under a crystalline neutron crust, is impossible to recreate in any laboratory on Earth, so scientists have been working up theories based on observations of the Crab Pulsar and other neutron stars.
Different theories predict different temperature ranges for such stars.
The high resolution camera aboard AXAF will help Weisskopf and other scientists test the theories by giving them a better reading of the temperature on the surface of the Crab Pulsar. Right now we're looking at the glow of activity near the center of the nebula as you might see the glow of city lights from a distance. Examining the pulsar in the center using AXAF will be like using a telescope to focus on a single street light in the middle of the city. The incoming radiation provides the extra kick and a shower of electrons is released, measured, and reconstructed into an image. In the HRC, this is done by two microchannel plates, thin sheets of lead oxide glass with microscopic holes at an angle to intercept X-rays which release an ever growing shower of electrons.