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The deep freeze at the edge of the solar system is well stocked. Just this year, for example, astronomers discovered a new dwarf planet there, along with a moon for another dwarf planet.
This zone of cold and darkness begins with the Kuiper Belt — a thick ring that extends well beyond the realm of Neptune, the most distant of the Sun’s major planets. It probably contains tens of millions of chunks of ice and rock, all of which were left over from the birth of the planets. And still more of these icy leftovers orbit beyond the Kuiper Belt.
So far, astronomers have actually seen only a couple of thousand objects in or beyond the Kuiper Belt. But several of them are big enough to classify as dwarf planets — including the most famous of them all, Pluto.
Earlier this year, a team using a telescope in Hawaii announced the discovery of a new dwarf planet. RR245 is probably about 400 miles in diameter. It follows a stretched out orbit that carries it more than 100 times farther from the Sun than Earth is. Right now, it’s moving toward the Sun, and will reach its closest point in about 80 years.
Also this year, another team used Hubble Space Telescope to discover a moon orbiting the dwarf planet Makemake, which is well beyond the orbit of Pluto. The moon is probably less than a hundred miles in diameter — roughly a tenth the diameter of Makemake.
These discoveries show that there’s still a lot to find in the deep freeze of the outer solar system.