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After a spectacular encounter with Pluto back in July, the New Horizons spacecraft will be directed toward a new target later this year. Like Pluto, the new target will be a member of the Kuiper Belt — a wide band of iceballs beyond the orbit of Neptune, the most-distant major planet. These objects are frozen leftovers from the birth of the planets.
Other stars have their own Kuiper Belts. One of the best examples is the bright star Fomalhaut. It climbs into view in the southeast by around 9 o’clock, and stands due south around midnight. There are no other bright stars around it, so it’s pretty easy to pick out.
Fomalhaut has at least one planet — one of the few exoplanets that’s ever been photographed. But Fomalhaut also has a giant disk of dust that orbits beyond the planet. The dust appears to be supplied by colliding comets — balls of rock and ice like those in the Kuiper Belt.
A study a few years ago said there are hundreds of billions to tens of trillions of comet-like objects in the belt around Fomalhaut. What’s more, up to a couple of thousand of them may collide every day. The smash-ups pulverize the colliding bodies, spraying out gas, dust, and rock. Over time, this material spreads out, helping to keep the disk full of fresh dust.
And coincidentally, this disk of material is about the same distance from Fomalhaut as the Kuiper Belt is from the Sun — a realm of icy bodies far from the star’s warmth.