Starting this weekend the Shoemaker-Levy 9 comet, identified in 1992 during its last visit to the solar system by Carolyn and Gene Shoemaker and their colleague David Levy, will collide with Jupiter. A detonation equivalent to millions of Hiroshima bombs is likely.
Series producer Tim Haines explains that the comet was "nicked from its orbit around the Sun" by the pull of Jupiter, and two years ago it came so close that the planet's gravity tugged it out into a "string of pearls" consisting of about 20 mountain-size rocks.
This time it will come even closer, explosively so. The Galileo satellite will have the ringside seat and though the impact will be on the "dark side" of the planet as far as we are concerned, scientific instruments will assess the phenomenon and perhaps detect a reflected flash.
Tonight's programme covers the exciting build-up to an event unparalleled in the history of astronomy. There will be brief follow-ups each weekday evening before Newsnight and on Friday The Crash Bash at 8.00pm reviews the events.

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