The Milky Way. Optical image showing part of the Milky Way from the constellation of Crux Australis (Southern Cross, bottom left) through Carina. It shows an area extremely rich in star clusters, dark and bright (pink) nebulae. Dark nebulae are formed by clouds of interstellar dust which scatter and absorb the radiation from stars situated behind them. Bright nebulae are clouds of interstellar gas which is ionised and lit up by the ultraviolet radiation of nearby hot and young stars. The Large Magellanic Cloud, a satellite galaxy of the Milky Way, is seen at bottom right. The brightest star at centre right is Canopus the second brightest star in the sky after Sirius.