The Crab Nebula: A Supernova
Remnant in Taurus
".....in the first year of
the period Chih-Ho, the fifth moon, the day of chi-ch'ou, a guest star
appeared approximately several inches south-east of Tien-Kuan......after
more than a year it gradually became invisible......"
This record of a "guest" star
appeared in the Annals of the Sung Dynasty. It was due to the sudden appearance
of a supernova witnessed by Chinese astronomers that occurred on July 4th
1054 AD . The star which reached mag -5 at its brightest could be seen
in broad daylight. This was equivalent to the light of 400 million suns!
The image below shows the remnant of that cataclysmic explosion some nine
hundred years later. The rate of expansion of the gas cloud amounts to
50 million miles/day.
This 4x40 sec exposure with 50cm f/4 imaged on 2000 January 24th
shows the intricate network of filaments resulting from this stellar
explosion . The fainter of the central pair of stars is the supernova remnant
that gave rise to this nebula. This star is not only an incredibly
dense neutron star, (1 cu. inch weighing 6 billion tons!) but is also rotating
at a rate of 30 times per second as evidenced by its radio emmission. It
was one of the primary candidates for the pulsars or pulsating
group of stars, which were discovered by Jocelyn Bell in 1967.
Check out the recent VLT
crab images from the newly commissioned 8 metre "Melipal" ESO
telescope from Chile, which were taken a few days after the image that
appears above. Also have a look here where
I have resampled and color coded the above image to the same scale as the
ESO image which shows some of the shock waves surrounding the pulsar.