Free Astronomy Magazine September-October 2016

T he Crab Neb- ula, which lies 6500 light- years away in the constellation of Tau- rus (The Bull), is the result of a super- nova — a colossal explosion that was the dying act of a massive star. Dur- ing this explosion most of the material that made up the star was blown into space at immense speeds, forming an expanding cloud of gas known as a su- pernova remnant. This extraordinary view of the nebula is one that has nev- er been seen be- fore. Unlike many popular images of this well-known object, which high- light the spectacular filaments in the outer regions, this image shows just the inner part of the nebula and combines three separate high- resolution images — each repre- sented in a different colour — taken around ten years apart. At the very centre of the Crab Neb- ula lies what remains of the inner- most core of the original star, now a strange and exotic object known as a neutron star. Made entirely of subatomic particles called neutrons, a neutron star has about the same mass as the Sun, but compressed into a sphere only a few tens of ki- lometres across. A typical neutron star spins incredibly fast and the one at the centre of the Crab Neb- ula is no exception, rotating approx- imately 30 times per second. The region around a neutron star is a showcase for extreme physi- cal processes and considerable vio- lence. The rapid motion of the ma- n T his two-colour image shows 2.7 x 2.7 degrees of the surroundings around the Crab Nebula. It was com- posed from Digitized Sky Survey 2 images. The brightest star is Zeta Tauri. [ESA/Hubble and Digitized Sky Survey 2] terial nearest to the star is revealed by the subtle rainbow of colours in this time-lapse image, the rainbow effect being due to the movement of material over the time between one image and another. Hubble’s sharp eye also captures the intricate details of the ionised gas, shown in red in this image, that forms a swirling medley of cavities and filaments. Inside this shell of ionised gas a ghostly blue glow sur- rounds the spinning neutron star. This glow is radiation given off by electrons spiralling in the powerful magnetic field around the star at nearly the speed of light . The supernova explosion from which the Crab Nebula was born was one of the first to be recorded in human history. This has made the Crab Nebula an invaluable object for the study of supernova rem- nants and has enabled astronomers to probe the lives and deaths of stars as never before.