NASA's Hubble Space Telescope has detected a long-sought population of comets known as the Kuiper belt that dwells at the icy fringe of the Solar System. The observation, which is the astronomical equivalent to finding the proverbial needle-in-a-haystack, bolsters proof for a primordial comet reservoir just beyond Neptune, currently the farthest planet from the Sun. On the basis of Hubble observations, astronomers estimate the belt contains at least 200 million comets that have remained essentially unchanged since the birth of the solar system 4.5 billion years ago. The region is thought to be the source of the comet that struck Jupiter in July 1994. “For the first time, we have a direct handle on the population of comets in this outer region. We now know, conclusively, that our solar system does not end at Neptune. The solar system just got a lot more interesting,” says Anita Cochran of the University of Texas, Austin.