G11.2-0.3 supernova remnant, Chandra X-ray image. The bright dot at centre is the core of a dead star. The outer layers of this star were blown away in the supernova explosion that took place as the star collapsed as it ran out of fuel. These outer layers are now seen as an expanding shell of gas and debris, forming what is called a supernova remnant (SNR). The different colours indicate the energy of the X-rays emitted as the expanding gases impact the interstellar medium, ranging from high (blue) through medium (green) to low (red). It is thought the supernova was the one observed around 2000 years ago. It is 16,000 light years from Earth in the constellation of Sagittarius. Image obtained by the Chandra X-ray Observatory (CXO).