Heart of the Crab
In July 1054 AD, astrologers observed a bright blue square in the sky near the sun at dawn. it was visible during the day for 3 weeks and at night for 2 years. 700 years later, the Crab Nebula became the first object in Charles Messier's famous catalog. In the 1940's astronomers calculated the expansion rate of the Crab Nebula and extrapolated back to definitively link the Crab Nebula to the ancient supernova (note motion in the core, more on that later):
as nebulae go, this is an odd one. it looks even more bizarre (and not particularly aesthetically pleasing) in narrow band.
there's just no rhyme or reason to it, a jumble of filaments in primary colors, psychedelic if nothing else:
it doesn't have the typical concentric rings of a supernova remnant:
https://picasaweb.google.com/lh/photo/s ... directlink
nor does it have the typical pillars and ionization fronts seen in emission nebulae:
https://picasaweb.google.com/lh/photo/0 ... directlink
so what's happening?
the bluer of the two central stars is a dense neutron star,
the remnant of the original star compressed so tightly that separate protons and electrons cannot exist
due to the conservation of angular momentum
the tiny neutron star is spinning at 30 cycles per second.
a strong magnetic field associated with the spinning star
accelerates electrons in the surrounding space to relativistic speeds ~half the speed of light!
collisions between the electrons and surrounding gas give off very high energy photons (strong x-ray source).
so what we have are filaments of gas surrounded by high energy photons, rather than a point source illuminating surrounding gas.
here's a closer view, you can see the neutron star (bluish of center pair)
get a sense of swirling whitish blue material around the central star
with red filaments illuminated by the surrounding light:
just for fun, i imaged this nebula for 2 months straight to see if i could catch anything moving at relativistic speeds. voila, you can see the motion in the animation (first image). here's a closer greyscale view with a linear stretch (and a bit more noise) for the purists in the crowd:
still more fun:
the crab nebula is 6,000 light years away.
2 good frames taken one month apart show bright wisp motion of 2 pixels in x and y at an image scale of .57 arcsec/px
sin(2.8 px x .57 "/px) x 6000 Ly / (1/12)y = .56 speed of light!
speed of electrons in the crab is quoted as about .5c
QED
OK i'm not really sure the moving wisps represent moving electrons
(love to get an answer),
but it's still pretty cool
but wait...there's more!
it just so happens that i imaged the crab back in 2006
so you can see the larger scale expansion here:
http://whwastro.homestead.com/files/cra ... k-800w.gif
note that the broad band whitish material appears to be expanding faster than the filaments
acceleration from the neutron star?
thanks for reading my post
and your consideration
-bill warden
astro.whwiii.net