The Crab Nebula, the stellar wreckage of a heavy weight star 7,000 light years away, that blew itself apart in a supernova explosion in the year 1054 that was recorded by Chinese and Arab astronomers. The supernova and its afterglow was actually visible in the daytime, the expired star blazing with the light of 400 million Suns. Being 4 times brighter than Venus it outshone everything else in the night sky except the Moon. It was also visible to the naked eye for 23 days in daytime, and 653 nights before fading away. The Crab Nebula was originally a star maybe 10 times more massive than the Sun. These larger stars tend to live only a few million years, burning up their stores of fuel at a rapid rate…they are live fast, die young stars. This star eventually came to the end of its short life in 1054, when the last of it’s fuel was used up in the core and the star was unable to support itself. At speeds of 70,000 kilometres per second the outer layers fell inwards quickly increasing the star’s density, compressing the core into pure neutrons, and heating it to a temperature of 6,000 times the centre of the Sun. This core was squeezed into an object that would fit into a small town at just 10 kilometres wide, at which point everything rebounded outwards in an extremely powerful explosion called a type 2 supernova.
In this supernova event most of the star’s material was then blasted out into space at a velocity of one tenth the speed of light. Riding ahead of this explosion was a shock wave that slammed into the interstellar medium causing it to glow brightly. To an observer in another galaxy this explosion would have outshone our entire Milky Way, releasing more energy than our Sun would emit in billions of years.
What was left behind in the heart of the destruction was a strange, incredibly dense object called the Crab Pulsar, a rapidly spinning highly magnetic neutron star just 10 kilometres across, but with a mass of between 1.4 and 2 times that of the Sun, (1.3 million Earth would fit into the volume of the Sun). A neutron star is so dense that on Earth just a teaspoon of it’s material would weigh 10 billion tonnes, it is 50 trillion times more dense than lead. This strange object is spinning at a rate of 30 times per second, this rapid spin creates a very strong magnetic field and this magnetic field spins with the star. The neutron star emits every type of radiation possible from gamma rays to radio waves. But the magnetic field squeezes this energy into two narrow beams, one out of the magnetic north and the other out of the magnetic south. Like a high speed galactic lighthouse the Crab Pulsar beam sweeps across space, one of the beams points in our direction as it spins so it appears as a flashing source of radiation as it crosses our line of sight. But it now appears that the Crab Pulsar hasn’t got just two beams, but four. Meaning it has two sets of magnetic poles, although one set is slightly weaker than the other. As the Crab Pulsar spins its magnetic field whips up sub atomic particles sending them flying out into space at close to the speed of light. Meanwhile intense winds are created that radiate out from the equatorial plane that slam into the surrounding nebula producing a termination shock.
In this deep x-ray image taken by the orbiting Chandra Observatory, the Crab Pulsar is at the centre of this otherworldly image. One of the jets of charged particles shoots out from the magnetic north pole, while the equatorial winds can be seen radiating outwards.
This video shows the winds and jets powered by the Crab Pulsar in X-rays taken by the Chandra X-Ray Observatory (left), and in optical light with the Hubble Space Telescope (right).
The tiny Crab pulsar is like an engine that powers the entire nebula, the spinning neutron star keeps the supernova remnant shining brighter than 75,000 Suns. Considering the Crab Nebula is 11 light years across, and the Crab Pulsar is just 10 kilometres wide, it is the equivalent of a single atom lighting up a square kilometre.
If this supernova had gone off 50 light years from Earth, it probably would have wiped out all life.
If the original star would have been more than 10 times more massive than the Sun, a black hole would have been created.
An object 10 kilometres across that spins at 30 times a second, 50 trillion times denser than lead, and made of pure neutrons…the universe contains some very strange phenomena.
