Better known as the Crab Nebula, M1 was first documented by John Bevis in 1731,
though it's discovery is most generally attributed to Charles Messier. Messier
actually observed the Crab Nebula on September 12, 1758 while observing the comet of
1758. M1 can be found ~1° northwest of Zeta Tauri.
M1 is the only supernova remnant in Messier's catalogue, and is relatively easy to
observe with minor magnification. Even with 7X35 binoculars, the Crab Nebula is
easy to see. Much more substantial magnification is needed to view the
individual components of the nebula. Though, in whole, M1 is roughly 11 light years by
7.5 light years, the center is a magnitude 16 pulsar that pulses every 0.033 seconds.
As it is relatively small, the pulsar can be difficult to view, but it is possible view
it with a 10-inch telescope in the right settings. An inner bubble of quick moving
particles constrained by the magnetic field of the pulsar can be discerned easily with a
6 or 8-inch telescope from a good site. The dense outer layer ejected by the supernova
is what is most commonly seen by the armchair astronomer.
Upon observation with a larger telescope, M1 appears to be broken into three segments
running northwest to souteast. The southern two segments are relatively similar in size
and brightness, but the northernmost segment is relatively small and dim. Along the
eastern edge of the nebula, an apparent indentation opens into a filament that runs
through the midsection of the nebula to the western side. A network of smaller
filaments surrounds the body of the nebula, indicating the presence of strong magnetic
fields. These structures were first observed in 1844, but have since been a topic of
discussion, as the Crab Nebula was photographed by the Hubble Space Telescope in 1994.
It was determined that the filaments of the nebula are veiled in glowing plasma. Data
from the HST also indicated that plasma pours back into the inner bubble of the nebula
in regions of magnetic instability. J. Jeff Hester of Arizona State suggested that the
glowing filaments of plasma form where the quickly moving material of the inner bubble
of the nebula pushes on the outer bubble. For more information, read Hester et
al in the January 1st, 1996 issue of Astrophysical Journal.
Apparently, M1 received its commonplace name 'Crab Nebula' in 1844 due to a drawing made
from observations at Birr Castle in Ireland. The drawing in question was said to look
somewhat like a horseshoe crab, though most accounts said otherwise.