How old is a 8-year-old on Jupiter?

About 0.67 Jupiter years old

On Earth we count years by Earth's orbit (about 365 days).Jupiter takes 4332.59 Earth days per orbit, so someone who has lived 8 Earth years has completed fewer full orbits — hence a different "age."

Jupiter spins faster than any other planet in the solar system - a day lasts only 9 hours 56 minutes!