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NASA spacecraft begins five-year trip to study Jupiter

CAPE CANAVERAL, Fla. -- A sun-powered robotic explorer named Juno is rocketing toward Jupiter on a fresh quest to discover the secret recipe for making planets.

Hundreds of scientists and their families and friends -- among thousands of invited guests -- cheered and yelled ''Go Juno!'' as the unmanned Atlas rocket blasted into a clear midday sky Friday. It will take five years to reach Jupiter, the solar system's most massive and ancient planet.

''Next stop is Jupiter,'' exulted Scott Bolton, Juno's principal investigator and an astrophysicist at Southwest Research Institute in San Antonio.

''It's fantastic!'' said Fran Bagenal, a planetary scientist at the University of Colorado at Boulder, who is also part of the NASA project. ''Huge relief all around.''

Within an hour of liftoff, Juno hurtled out of Earth's orbit at 24,000 mph on a roundabout course for Jupiter. It was expected to whip past the orbit of the moon in half a day, or early this morning.

It is the first step in Juno's 1.7 billion-mile voyage to the gas giant Jupiter, just two planets away but altogether different from Earth and next-door neighbor Mars.

Juno is solar powered, a first for a spacecraft meant to roam so far from the sun. The three huge solar panels popped open an hour into the flight, each one stretching as long and wide as a tractor-trailer. Previous spacecraft to the outer planets have relied on nuclear energy.

With Juno, scientists hope to answer some of the most fundamental questions of our solar system.

''How Jupiter formed. How it evolved. What really happened early in the solar system that eventually led to all of us,'' Bolton said earlier in the week.

Bolton said Jupiter is like a time capsule. It got most of the leftovers from the sun's creation nearly 5 billion years ago -- hence the planet's immense size -- and its enormous gravity field has enabled it to hold onto that original material.