Fig11_13 Crab Nebula

Fig11_13 Crab Nebula

Fig. 11.13 . The optically visible light of the Crab Nebula, designated as M 1 and NGC 1952, consists of two distinct parts. A system of expanding filaments forms an outer envelope in which emission lines occur at well-defined wavelengths; an inner amorphous region emits continuum radiation at all wavelengths. A Type II supernova explosion observed nearly 1,000 years ago, in 1054, ejected the filaments. The expanding filaments shine mostly in the light of hydrogen (orange), but also include the light of neutral oxygen (blue), singly ionized sulfur (green) and doubly ionized oxygen (red). The blue-white continuum glow that is concentrated in the inner parts of the nebula is the non-thermal radiation of high-speed electrons spiraling in magnetic fields. This continuum emission is powered by a spinning neutron star, the south westernmost (bottom right) of the two central stars. The neutron star is the crushed, ultra-dense core of the exploded star. It is also a radio pulsar that acts like a lighthouse spinning 30 times a second. (Courtesy of NASA/ESA/J. Hester and A. Loll, ASU.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University