The next post on my Geological Fun Fact series:
Comet tails do not always follow behind a comet. The tail is actually only produced near a star (such as our sun). When the comet gets close enough to the sun, the solar winds
push debris off of the comet. This produces the comet tail. However, instead of following behind the comet, the tail always points away from the sun. So if the comet is going towards the sun, the tail is behind, but if the comet is going away from the sun, the tail is in front.