Juno is a spacecraft launched by NASA on August 5, 2011, to study the planet Jupiter and its moons. The spacecraft is named after the Roman goddess Juno, who was the wife of Jupiter. It is the second spacecraft to be sent to Jupiter, after Galileo.
Juno will orbit Jupiter 37 times over the course of 20 months, getting closer to the planet than any other spacecraft has before. Juno will help us understand how Jupiter formed and how our solar system evolved.
Jupiter is the largest planet in our solar system. It is more than twice as massive as all of the other planets combined. Jupiter is made mostly of hydrogen and helium gas. It doesn’t have a solid surface like Earth does; if you tried to stand on Jupiter, you would just sink into its atmosphere forever.
The gravity on Jupiter is much stronger than it is on Earth. If you weighed 100 pounds on Earth, you would weigh 240 pounds on Jupiter. The pressure at the core of Jupiter is also very high—about 24 million times higher than atmospheric pressure on Earth!
Despite its size and gravity, Jupiter rotates very quickly—once every 10 hours or so. This quick rotation flattens out the planet at its poles and bulges it out at its equator. As a result, Jupiter’s diameter at its equator is about 10% wider than its diameter at its poles!
Jupiter has a faint ring system that was discovered in 1979 by Voyager 1 (a space probe launched by NASA). The rings are made up of tiny particles of dust that are thought to be left over from comets or asteroids that have been torn apart by Jovian gravity as they passed too close to the planet.