Pluto proves larger than previously thought

CAPE CANAVERAL, Fla. – Little Pluto is a little bigger than anyone imagined.

On the eve of NASA’s historic flyby of Pluto, scientists announced Monday the New Horizons spacecraft has nailed the size of the faraway icy world.

Measurements by the spacecraft set to sweep past Pluto today indicate the diameter of the dwarf planet is 1,473 miles, plus or minus 12 miles. That’s about 50 miles bigger than previous estimates in the low range.

Principal scientist Alan Stern said this means Pluto has a lower density than thought, which could mean an icier and less rocky interior.

New Horizons’ 3 billion-mile, 9 1/2-year journey from Cape Canaveral, Florida, culminates this morning when the spacecraft zooms within 7,767 miles of Pluto at 31,000 mph.

“It sounds like science fiction, but it’s not,” Stern said as he opened a news conference at mission headquarters in Maryland. “Tomorrow morning, a United States spacecraft will fly by the Pluto system and make history.”

Discovered in 1930, Pluto is the last planet in our solar system to be explored. It was a full-fledged planet when New Horizons rocketed away in 2006, only to become demoted to dwarf status later that year.

New Horizons already has beamed back the best-ever images of Pluto and big moon Charon on the far fringes of the solar system.

With the encounter finally at hand, it all seems surreal for the New Horizons team gathered at Johns Hopkins University’s Applied Physics Laboratory.

Three new discoveries were revealed Monday, a tantalizing sneak preview as the countdown to closest approach reached the 21-hour mark.

Besides the revised size of Pluto – still a solar system runt, not even one-fifth the size of Earth – scientists have confirmed that Pluto’s north pole is indeed icy as had been suspected. It’s packed with methane and nitrogen ice.

And traces of Pluto’s nitrogen-rich atmosphere have been found farther from the dwarf planet than anticipated. New Horizons detected lost nitrogen nearly a week ago.