People in some of Australia's southern states could witness the Aurora Australis tonight. According to the Bureau of Meteorology, the dazzling Southern Lights may appear in the sky over Tasmania on Friday night and could also be visible in far southern Victoria. The phenomenon occurs when charged particles emitted by the sun reach Earth and interact with gases in our atmosphere. The colour of the display is determined by the gases involved in this process. Oxygen causes green and sometimes red (this is rare) and Nitrogen can produce blue or purple lights. Unfortunately, cloud cover may hinder the view tonight thanks to an upper level low pressure system moving over Victoria. The best chance of clear skies will be in southern Tasmania early in the evening away from anthropogenic light pollution.