ALMOST A THOUSAND YEARS AGO, on July 4 in the year 1054 CE, astronomers in China and the Middle East noticed a bright new star in the night sky. It appeared in the constellation Taurus, and remained visible for roughly two years.
They couldn’t have known what it really was—a supernova, a titanic stellar explosion that occurred when a massive star reached the end of its life. The explosion was matched by an implosion, which crushed the star’s core and produced a neutron star—made of matter so dense that the atoms’ electrons were forced into their nuclei and combined with the protons to form more neutrons.
The density is so high, that a teaspoon of neutron star material has as much mass as 900 Great Pyramids.
And the neutron star is spinning, making it a pulsar…so called because the natural radiation it emits is sent out along beams, which sweep across our field of view like a lighthouse, seeming to pulse on and off.
So much for the implosion. The explosion hurled enormous quantities of gas into space, eventually forming the glowing cloud, or supernova remnant, we see today. On early photographs, which didn’t show much detail, the nebula looked very crab-like, hence its name.
The distance to the Crab Nebula is a bit uncertain, but it’s probably around 6,300 light-years away. And the cloud is expanding at a speed of 1,500 kilometres per second!
Download a 1280 x 1280 wallpaper image of the Crab Nebula here.
Story by Jonathan Nally. Image courtesy NASA, ESA and Allison Loll/Jeff Hester (Arizona State University). Image acknowledgement: Davide De Martin (ESA/Hubble).
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