THE CRAB NEBULA M1
This is a color composite formed from two images of the well-known Crab Nebula, taken on the night of October 27th 1995 with the NOAO/STIS/Tektronix 2048x2048 CCD detector on the 3.5-meter WIYN telescope. At the focal plane of the WIYN, this detector has a sampling scale of 0.2 arc seconds per pixel. This picture shows the full imaging power of the WIYN telescope: the "seeing", or image size, is about 0.6 arc seconds, or about twice the resolution of typical ground-based images. Some shell-like features in the center of the nebula, and the subtle filamentary structure evident throughout the region, are impossible to see in fuzzier (that is, more typical) pictures. Image processing can reveal even more detail.
About this object
The Crab Nebula was originally given this name due to its resemblance to a crab's claw in
an early sketch made in 1855 by Lord Rosse's staff astronomer R.J. Mitchell. It is the
remnant of a supernova explosion in the year 1054 A.D., which was recorded in five
separate accounts in the Far East, although, oddly, no western observation has survived.
The nebula was probably first noticed in 1731 by John Bevis, and it was significant enough
to be the first entry in Charles Messier's list of nebulae (compiled to avoid mistaking
them for comets). The nebula continues to expand and change the details of its appearance,
and this is partly due to the violence of the original explosion. However, the star which
exploded left behind a rotating neutron star, which continues to beam energy out into the
nebula, as well as flashing with a period of only 33 milliseconds. The details of this
energy input are important for our understanding both of neutron stars and of the physical
conditions in the nebula, and are revealed in the patterns of filaments, their brightness
and colors, and the way they change with time.
Jay Gallagher (U. Wisconsin)/WIYN/NOAO/NSF
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