CAPE CANAVERAL, Fla. (KRON/AP) – On the eve of NASA’s historic flyby of Pluto, scientists are revealing new information about the mysterious dwarf planet: It turns out “Little Pluto” is a little bigger than anyone imagined.

Scientists announced on Monday that the New Horizons spacecraft has been able to pinpoint the size of the faraway icy world. They say measurements indicate the radius of the planet spans 736 miles, plus or minus six miles. That’s 20 miles to 30 miles bigger than previous estimates. The diameter would be twice that.

Principal scientist Alan Stern says this means Pluto has a lower density than previously believed, which could mean an icier interior.

Tuesday morning’s long-awaited historic flyby of the solar system’s little known planet will be the culmination of New Horizons’ 3 billion-mile, 9½-year journey. The spacecraft is set to zoom within 7,767 miles of Pluto. Scientists say there’s only one chance in 10,000 something could go wrong, like a debris strike.