世纪彗星 / 2013 HD

Comet ISON could well be the brightest and most spectacular comet for a generation. It should appear above the eastern horizon from December 2013 as a glorious streak across the sky. ISON has been travelling towards the sun for ten thousand years and will make only one orbit through its corona before disappearing off into the outer solar system.　　But as well as providing a great...