Chandra Release - February 27, 2003

Visual Description: B1957+20

 An X-ray and optical image of the pulsar B1957+20 is displayed. The image is dominated by shades of black, blue, red and green.  Pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation in the form of pulses. In the image, the object has a distinctive structure, like a red comet in a green wake amidst a sea of blue blobs. The structure is an elongated cloud, or cocoon, of high-energy particles flowing behind the rapidly rotating pulsar, B1957+20 (a bright white point-like source at the tip of the red shape). The object, a.k.a. the "Black Widow" pulsar, is moving through our galaxy at a speed of almost a million kilometers per hour. The bow shock wave due to this motion is visible to optical telescopes, shown in this image as a greenish crescent shape. The pressure behind the bow shock creates a second shock wave that sweeps the cloud of high-energy particles back from the pulsar to form the cocoon.