Something very odd seems to be going on out beyond Pluto. Astronomers have known for more than two decades that the tiny former planet is not alone at the edge of the solar system: it is part of a vast cloud of icy objects known collectively as the Kuiper belt. But unlike most of their fellow travelers, and unlike the planets and most asteroids, which orbit between Mars and Jupiter, a small handful of Kuiper belt objects, or KBOs, have orbits that are decidedly weird.
In the mid-1990s, astronomers made history when they detected three planets orbiting stars in the Milky Way. The planets were nothing like Earth, however: They were giant gas balls like Jupiter or Saturn. More than 500 planets have been found since then, yet none of them could support life. Now, armed with more powerful technology, planet hunters are racing to find a true twin of Earth. Science writer Michael Lemonick has unique access to these exoplaneteers, as they call themselves, and Mirror Earth unveils their passionate quest.
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Spacecraft will get an up-close look at comets, asteroids, and dwarf planets from the distant Kuiper belt.