Comet McNaught
17-18 Jan, 2007
John Archer 10 Pearce Place, Waiouru, New Zealand

This is much bigger than the meteors we see hitting the atmosphere 50 km above us. This comet was 126 million kilometres from Earth in these photos. At the core of its head is a lump of ice and rock about 30 km across. The heat of the sun is vapourising tons of ice every second and the vapour is throwing the rocks out into a head about 1.5 million km across. Then the force of the radiation from the sun (the solar wind) is pushing the cloud of rocks away behind it. The brightest part of this tail is about 10 million km long, and the broader and more faintly glowing plume seen above that is about another 20 million km long.