NASA's unmanned Juno spacecraft on Monday began orbiting Jupiter, a key triumph for a $1.1 billion mission that aims to uncover the origins of the biggest planet in the solar system.

"Welcome to Jupiter," said a commentator at mission control at NASA's Jet Propulsion Laboratory in Pasadena, California.

The room erupted in cheers as the solar observatory, which has traveled 1.7 billion miles (2.7 billion kilometers) since it launched five years ago from Cape Canaveral, Florida, successfully entered its aimed-for orbit around Jupiter at 11:53 pm (0353 GMT Tuesday).