Beating heart of Crab Nebula
Monday 11 July 2016
Analysis for The Conversation by Dr Alan Duffy, Swinburne University of Technology
In 1054 a new star appeared in the night sky and was noted by Chinese astronomers before fading away again after several years. These meticulous astronomers would have been astounded by their modern day counterparts who used an orbiting space telescope (NASA’s Hubble) to peer into the heart of this object a thousand years later.
The latest release from Hubble has snapshots every decade superimposed in a different colour revealing a central rainbow as rapidly moving material streams from the very heart of the nebula. The initial expulsion of material (seen as reddish wisps) was from the exploding star itself. The massive star was around ten times the mass of our Sun and when it exhausted its fuel supplies imploded under the immense gravity. As the material fell onto the dense core of the star it both crushed the centre to densities only seen in atomic nuclei (forming a neutron star) and rebounded the infalling material in a titanic explosion visible thousands of lights away on Earth.
At the heart of the nebula is the astoundingly dense `dead core' of the massive progenitor star known as a pulsar. Imagine crushing the mass of a Sun into something the size of a city. Now picture it with beams of radiation / jets blasting outwards from the magnetic poles. Then set the entire object spinning 30 times a second like a kitchen blender so that these beams sweep across the Earth like a lighthouse. Many of these pulsars were discovered by Australia’s radio telescopes at the ATNF which keeps records of their regular clockwork ticking (although some like the Crab Pulsar are incredibly annoying like a mosquitto).
A pulsar is an extreme object and a fantastic way to test the boundaries of physics, everything from trying to measure gravitational waves, the nature of matter itself at its limits and even detecting diamond planets in orbit around them.
No wonder astronomers get so excited about these close up views of such a fascinating object.