Juno enters Jupiter's orbit: probe reaches solar system’s gas giant

Juno enters Jupiter's orbit: probe reaches solar system’s gas giant

After a five-year, 2.8 billion km journey, Nasa’s spacecraft Juno finally entered orbit of Jupiter, the biggest planet in the Milky Way

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This Atlas rocket launched Juno almost five years ago.
Photo: AP

Nasa’s Juno spacecraft reached Jupiter on Monday after a five-year voyage to begin exploring the king of the planets.

Ground controllers erupted in applause when the solar-powered spacecraft beamed home news that it was circling Jupiter’s poles.

As Juno approached the planet, it fired a rocket engine to slow itself down, and gently slipped into orbit. Because of the communication time lag between Jupiter and Earth, Juno was on autopilot when it executed the daring move.

The spacecraft’s camera and other instruments were switched off for arrival, but hours before the encounter, Nasa released a series of images taken last week, showing Jupiter glowing in the distance, circled by its four inner moons.

Scientists have promised close-up views of the planet during the 20-month, US$1.1 billion mission.

The fifth rock from the sun and the biggest planet in the solar system, Jupiter is what’s known as a gas giant – a ball of hydrogen and helium – unlike rocky Earth and Mars. Jupiter is an extreme world that probably formed first, shortly after the sun. Unlocking its history may hold clues to understanding how Earth and the rest of the solar system developed.

Juno’s mission: to peer through Jupiter’s clouded atmosphere and map the interior from a unique vantage point above the poles. Among the lingering questions: How much water exists? Is there a solid core? Why are Jupiter’s southern and northern lights the brightest in the solar system?

“What Juno’s about is looking beneath that surface,” Juno chief scientist Scott Bolton said before the arrival. “We’ve got to go down and look at what’s inside, see how it’s built, how deep these features go, learn about its real secrets.”

In the coming days, Juno will restart its instruments, but the real work won’t begin until late August when the spacecraft swings in within 5,000km of Jupiter’s clouds.

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