APOD 3.7

This is an image of Cassiopeia A, which is a supernova remnant that appeared about 300 years ago. In this picture, which is a composite of X-ray and visible light. It spans about 11,000 light years across, which is relatively small for a nebula, but it is rapidly expanding because it was recently formed. This image is even more astounding because you can actually see the light from the neutron star. This star is only a few miles across, which means it has very little surface area, but the fact that it can be seen from Earth means that it is extremely bright. Another interesting fact about this neutron star is that it is forming a super-fluid that is frictionless. Nothing on Earth could possibly compare to this material, but that fact that it exists in the Universe is astounding.