The team will also continue the long-term, precise timing of the pulsar. Measuring the change of its orbit more precisely may allow the astronomers to determine if there is a 'classical' component to the effect, which would clearly imply a main sequence star rather than a black hole. A pulsar is the collapsed core of a massive star that has ended its life in a supernova explosion. Weighing more than our Sun, yet only 20 kilometres across, these incredibly dense objects produce beams of radio waves which sweep round the sky like a lighthouse, often hundreds of times a second. Radio telescopes receive a regular train of pulses as the beam repeatedly crosses the Earth so the objects are observed as a pulsating radio signal.
Pulsars make exceptional clocks, which enable a number of unique astronomical experiments.
The triumphs and tragedies of the space program are recalled by those who were there in this glossy 240-page book from the Discovery Channel. Next Launch A Lockheed Martin Athena 1 will launch the Kodiak Star mission for NASA and the Air Force no sooner than Saturday from Kodiak Island, Alaska. Visit the Tracking Station for a full listing of upcoming launches. In this 2001 calendar, John Sexton turns the space shuttle into an art form with his unique black and white photographs of the hardware.