Two X-ray images of the Crab Nebula (M1, NGC 1952) taken by the Einstein Observatory X-ray satellite, showing the Crab Pulsar in its on & off phases. The Crab Nebula is a supernova remnant about 6000 light years away in the constellation of Taurus. It is the remnant of a catastrophic stellar explosion observed by Chinese & Japanese astron- omers in 1054 AD. The bright spot on the left image is the pulsar, a rapidly spinning neutron star which is the tiny, dense remnant of the star which exploded. The pulsar is only 10 km in radius & rotates 30 times each second, flashing each time one of the magnetic poles points towards Earth.