Hyakutake!

The extremely close approach of comet C/1996 B2 (Hyakutake) in March provided a unique opportunity to learn more about these visitors from the distant parts of the solar system. Although the comet was only discovered on 30 January by Japanese amateur astronomer Yuji Hyakutake, we were extremely lucky this time because of the great improvements in ground and orbit based instrumentation since the last close approach of a comet, IRAS-Araki-Alcock, over a decade ago. The close passage by Earth of a comet (in this case only 0.1 AU) obviously provides superior spatial resolution and higher signal-to-noise observations than would otherwise be possible. This is especially important in the study of comets, however, as some of the parent molecules of coma species in comets are extremely short lived and decay very close to the nucleus, and thus can only be observed at close range. High spatial resolution especially benefits the observation of rapid changes in the inner coma, allowing us to see what is going on much closer to the nucleus, itself. Overall, combining ovservations over a large spectral range taken with different techniques will greatly enhance our knowledge of activity mechanisms and the chemical composition of comets. The larger goal is gaining insight into the physical conditions during the formation of the early solar system. In this way, comets are visitors from the distant past of the solar system as well.