| The
Crab Nebula consists of a pulsar, a rapidly rotating neutron star at the
center, surrounded by a bright diffuse nebula. The nebula, which is about
six light years across, is expanding outward at 3 million miles per hour.
The filamentary system visible in the optical images is near the outer boundary
of this expansion. Both the nebula and the pulsar are bright sources of
radiation in all wavelengths.
The radiation we observe from the Crab Nebula is produced mainly by
high-energy particles accelerated by the neutron star. These energetic
particles, which near the neutron star are thought to include anti-matter
positrons as well as electrons, spiral around magnetic field lines in
the nebula and give off radiation by the "synchrotron" process.
|
 |
Comparing
the x-ray, optical, infrared, and radio images of the Crab shows that the
nebula appears most compact in X-rays and largest in the radio. The X-ray
nebula shown in the Chandra image is about 40% as large as the optical nebula,
which is in turn about 80% as large as the radio image. This can be understood
by following the history of energetic electrons produced by the neutron
star. Electrons with very high energies radiate mostly X-rays. |
|
