Cheap ways to travel for The longest known comet tails in space are Hyakutake’s at AU million km, that of Messier’s Comet of at AU million km, and that of the Great March Comet of at AU million km. See fig. As regards the apparent lengths of comets in history, the longest is a -degree one recorded in the year AD by the Chinese C/ K. -degree comets were seen in AD and Tebbutt’s Comet of was degrees long, suficient to extend two-thirds of the way across the dome of the sky. Great comets in and , as well as Halley’s Comet in AD , were longer than degrees, and many other comets in history peaked at degrees e.g. [Halley , The apparent length of a comet is determined not just by the actual tail length but also by the comet’s brightness, its distance from Earth, and the angle of the comet relative to the Sun and Earth. Cheap ways to travel 2016.