Hyakutake is one of the most active comet to pass this close to the Earth in over 400 years, and probably will become the brightest naked-eye comet in two decades, so astronomers say that this opportunity is unlikely to be repeated during Hubble's remaining lifetime. Researchers will view the first Hubble comet images on March 26th and, allowing time for reviewing and preparing the data, hope to have an image which NASA and the Space Telescope Science Institute will make available to media representatives no later than March 28. A media advisory will be issued to announce availability of the image. Viewing the deep-space visitor will be especially tricky because the comet's position is relatively poorly determined and Hubble's instruments can only view small portions of the sky. At its closest approach, on March 25, the comet will be moving along at nearly one arcsecond per second, which means that it will cover the width of the full Moon in about 40 minutes.
Astronomers expect to see details as small as four miles across with Hubble.
Weaver also hopes to see jets of dust in the Hubble images. These spectra should be at least ten times more sensitive than previously obtained ultraviolet spectra of comets and, hopefully, will reveal new molecules which have previously been inaccessible. The comet captures the magnetic field out of the solar wind, a stream of subatomic particles from the Sun. Near the nucleus, the field should wrap around in a hairpin configuration, and also should show a pileup region on the sunward side of the nucleus. Water in the Comet On April 3rd and 4th a team of scientists, lead by Dr. Michael Combi of the University of Michigan's Space Physics Research Laboratory, will use three of Hubble's instruments, as well as coordinated ground-based telescope observations, to study water photochemistry on the comet, which is important for interpreting a variety of observations of comets.