Quaoar

The object known as Quaoar is in a bit of limbo. It’ll probably be designated as a dwarf planet — an object similar to Pluto. One key factor in determining its qualification as a dwarf planet is its size. Estimates have ranged by quite a bit. But some observations made last year are helping narrow that range.
Artist's concept of Quaoar [NASA]Measuring Quaoar’s size is difficult in part because it’s a long way out — close to four billion miles. And no matter what its exact size is, it’s small — probably no more than a third the diameter of the Moon. Measuring something that small at such a great range is tough. So estimates have ranged from about 525 to 775 miles.
Astronomers have used several techniques to zero in on Quaoar’s size. For one, they’ve used Hubble Space Telescope to make a physical measurement of its size. Since Hubble is above Earth’s blurring atmosphere, it sees objects more clearly than most ground-based telescopes, so it produces better size measurements.
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