what are planets made up of
The four planets closest to the Sun are largely made up of rock, like the Earth, and are called the terrestrial (Earth-like) planets. The next four planets are much larger and made mainly from hydrogen and helium. They are often called gas giants. Pluto is different still, a deep-frozen world of rock and ice.LANETS. A planet is a world that orbits a star. There are nine planets circling around the SunâMercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. They take different amounts of time to orbit the Sun, from only 88 days for Mercury to nearly 250 years for Pluto.