Nasa's probe Juno is going to reach Jupiter today, and that's awesome because we know so little about our solar-system giant. Here's what we do know:
- Named for the king of the Roman gods, Jupiter is one of five planets visible with the naked eye. It's so massive that it could hold everything else in the solar system, minus the sun.
- Like the sun, Jupiter is a ball of mostly hydrogen and helium. It was probably the first planet to form. Jupiter is 11 times wider than Earth and 300 times heavier.
- Swirling storms. Dusty rings. Glowing polar lights. Glimpses of Jupiter have been beamed back by robotic explorers since the 1970s. Most visits were brief and only one spacecraft spent time circling the planet. So there's still lots to learn about the biggest planet in the solar system and its four main moons.
Jupiter is the fastest-spinning planet in the solar system, taking just 10 hours to complete a rotation.
As Jupiter spins, it drags its magnetic field around with it, causing the most spectacular auroras in the solar system.