The spectacular sight of Comet Hyakutake
moves through the constellation Boötes in this series of images. At
the bottom of this page is a close-up comparison of the coma (the comet's
head), in which you can actually see the comet's movement through the background
stars.
On the night of March 23rd, 1996, 2 days before
its closest approach to earth, Comet Hyakutake was heading north through
Boötes the Herdsman on its way to a close rendezvous with Polaris,
the North Star. In each of these images the bright star Arcturus is visible
at the far right. The bright star the comet is racing past is Epsilon Boötis.
At the time, Comet Hyakutake was roughly 15 million kilometers from Earth
(that's only 1/10th the Earth-Sun distance).
Most comets don't ever get that close! Because
of Hyakutake's relatively short distance from Earth, it appeared to move
quickly through the sky. At the time of these images, the comet was moving
roughly 10 degrees per day (10 degrees in the sky is the width of your
fist held at arm's length), or approximately 0.4 degrees per hour. This
is roughly the same rate the moon moves with respect to the background
stars. While this is hardly what we would call fast, in astronomical
terms Hyakutake was speeding! When the comet was near a bright star as
in this image, it was possible to see its motion over the course of an
hour (the same is true of the moon). Through a telescope the motion was
even more dramatic.
Compare the comet's motion against the background
stars: