ABSTRACT
The Crab Nebula, the SNR that resulted from a supernova explosion some 900 years ago, is one of the most important sources in high energy astrophysics. It has been said that half of all high energy astrophysics can be found in the Crab Nebula. As one of the few sources that has been observed for nearly a millennium, and at all wavelengths from longwave radio to VHE gamma rays, it is the best studied source in the cosmos. It was one of the first radio sources detected, it is one of the strongest x-ray sources, it was the first SNR to be clearly identified with a pulsar, it was one of the first gamma-ray sources detected (from balloonborne telescopes), and it continues to provide glimpses of new astrophysical processes. For a time it was the fastest known radio pulsar (33 ms); at many wavelengths the radiation from the pulsar dominates the nebular emission. At optical wavelengths it is extraordinarily complex with many different phenomena superimposed (figure 6.1). It was the prototype source for synchrotron radiation by cosmic electrons [19] and is the prototype for Compton-synchrotron emission from cosmic sources [9]. Although generally seen as a strong and steady source, it is variable on time scales of days in the complex volume near the pulsar.
