Hyakutake

Bright, fast-moving comet discovered by Japanese amateur astronomer Yuji Hyakutake in January 1996. The comet became a spectacular sight only two months later. It passed within 15 million km/9 million mi of the Earth on 25 March, one of the closest approaches of a comet in recent history, and within 34 million km/21 million mi of the Sun on 1 May. At its brightest, in mid-April, its broad head reached zero magnitude and its long, narrow tail stretched 100° across the sky. The Ulysses spacecraft passed through the tail of Hyakutake in 1996. Analysis of data from that flight revealed in March 2000 that Hyakutake's tail is 550 million km/342 million mi long, making it the longest comet tail known.