Supernova remnant. Coloured X-ray image of a compact nebula around the Vela pulsar. The bow- like structures are thought to be shock waves due to matter rushing away from the central neutron star colliding with gas thrown out by a supernova explosion some 12,000 years ago. The motion of the star through the surrounding gas results in the swept-back appearance of the nebula. The Vela pulsar is about 1500 light years from Earth. This image was made by the Chandra X-ray Observatory in Earth orbit.