Pluto is bigger and icier than expected

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BOULDER, Colo. — NASA’s New Horizons spacecraft "phoned home" Tuesday night when it signaled a successful flyby of the dwarf planet Pluto.

The craft left Earth nearly a decade ago and traveled more than 3 billion miles.

In Boulder hundreds gathered at the University of Colorado's Fiske Planetarium to celebrate the monumental occasion.

“We’re there and it’s really exciting!” said Doug Duncan, director of the planetarium.

Duncan has been studying Pluto for a long time. Like most scientists, he knew the planet was tiny, he knew it was cold and he knew it was far out there. But after New Horizons sent back initial data, scientists including Duncan learned a few more things.

“Pluto is a little bit bigger than we thought,” he said.

The dwarf planet is roughly twice the size of Texas. Its temperature is somewhere around minus-400 degrees Fahrenheit. Seeing as how it’s a cold planet, scientists have also discovered it consists more of ice instead of rock.

“So we’re learning some more clues about what’s inside just from the fact it’s little bit bigger,” Duncan said.

What’s also interesting, Duncan said, is there are about 100 other Pluto-like dwarf planets near it in the outer-galaxy.

“The planet Neptune has a moon called Triton and Triton is a twin of Pluto. It used to live out near Pluto and it came in too close to Neptune and got captured,” Duncan said.

On Wednesday, NASA is hoping to learn more about what Pluto is made of. Scientists will be able to tell based on Pluto’s color and spectrum.

“Once we analyze the spectrum and the gases we’ll be able to tell you pretty precisely what Pluto is made of,” Duncan said.