“That settles the debate about the largest object in the Kuiper Belt,” New Horizons lead scientist Alan Stern, with the Southwest Research Institute in Boulder, Colo., told reporters Monday.
The observations, relayed as New Horizons neared Pluto after a 9.5-year, 3 billion mile journey, show that Pluto spans about 1,473 miles in diameter. Scientists suspect the maximum diameter for Eris, which circles the sun about three times farther than Pluto, is 1,445 miles.
Pluto’s size has been somewhat of a mystery because the planet’s atmosphere makes it somewhat blurry against the light of background stars, which are used as measurement tools.
With a slightly larger diameter than predicted, Pluto is a little less dense, with a higher percentage of ice and a little less rock. The measurement also means Pluto’s troposphere, its lowest layer of atmosphere, is closer to the ground than some computer models predict.
Early analysis of New Horizons data also shows that more of Pluto’s nitrogen atmosphere is escaping into space, or an unknown transport mechanism is ramping-up the process. On Tuesday, New Horizons will be able to see if Pluto is sharing any of its atmosphere with its primary moon and orbital partner Charon.
The discoveries are just a hint of what scientists expect from New Horizons as it punches through the Pluto system Tuesday morning, then looks back at its quarry for several more hours.
“This science is already mouth-watering,” Stern said.
Although within 650,000 miles of Pluto, the difference between what New Horizons’ cameras saw on Monday and what they will image when the spacecraft passes about 7,750 miles from Pluto (and about 18,000 miles from Charon) on Tuesday. Image resolution will jump from 15 kilometers per pixel to less than 100 meters, an improvement of more than two orders of magnitude, Stern said.
Read more at Discovery News
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