Jupiter is the largest planet in the solar system and the fifth in terms of distance from the Sun. It is one of the brightest objects in the night sky, rivalled only by the Moon, Venus, and, on rare occasions, Mars. Jupiter is represented by the symbol ♃. When ancient astronomers named Jupiter after the Roman ruler of the gods and heavens (also known as Jove), they had no idea of the planet's true size, but the name is appropriate because Jupiter is larger than all the other planets combined. It takes nearly 12 Earth years to orbit the Sun and rotates once every 10 hours, which is more than twice as fast as Earth; its colourful cloud bands can be seen with a small telescope.It has a narrow ring system and 79 known moons, one larger than Mercury and three larger than Earth's Moon. Some astronomers believe Jupiter's moon Europa may be hiding an ocean of warm water—and possibly even life—below its icy crust.