Pulsar. Satellite image of a shock wave (yellow) at the 'head' of pulsar G359.23-0.82. The pulsar (blue), also known as the Mouse because of its shape, travels at 2.1 million kilometres per hour. A pulsar is a rapidly spinning, highly magnetised neutron star that generates winds of high energy matter and anti-matter particles. These particles create large, magnetised clouds of high energy particles called pulsar wind nebulae. This image will allow astronomers to make the first detailed study of the behaviour of high-energy particles around a fast moving pulsar. Image taken on 23 October 2003 by the Advanced CCD Imaging Spectrometer (ACIS) aboard NASA's Chandra X-ray observatory.