A solar-powered spacecraft, with three special passengers onboard, is currently spinning toward Jupiter for the closest encounter with the biggest planet in our solar system.

Nasa's Juno spacecraft is set to fire its main rocket engine around 3.15pm to slow itself down from a speed of 265,000 kph and slip into orbit around Jupiter.

Hitching a ride are three 1.5-inch Lego figures depicting the 17th century Italian astronomer Galileo Galilei, the Roman god Jupiter, and the deity's wife Juno - all made from aluminium to withstand the Jupiter's harsh environment.

In Greek and Roman mythology, Jupiter drew a veil of clouds around himself to hide his mischief. From Mount Olympus, Juno was able to peer through the clouds and reveal Jupiter's true nature.

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Juno holds a magnifying glass to signify her search for the truth, while her husband holds a lightning bolt.

The third Lego crew member is Galileo Galilei, who made several important discoveries about Jupiter. He used a telescope to confirm the phases of Venus and discovered the four largest satellites of Jupiter - named the Galilean moons in his honour.

"Of course, the minifigure Galileo has his telescope with him on the journey," Lego said in a statement.

By drawing attention to these Lego characters, Nasa aims to inspire the next generation of spacecraft engineers by encouraging children to explore subjects such as science and technology.

Juno, along with its three passengers, meets its demise in 2018 when it deliberately dives into Jupiter's atmosphere and disintegrates - a necessary sacrifice to prevent any chance of accidentally crashing into the planet's potentially habitable moons.