Do other planets have moons?
Apart from the Earth, most of the other planets have moons although these are usually quite small. Saturn has the most moons — it has at least 18. Some of these are very strange. Enceladus has a smooth surface covered with shiny beads of ice that make it shine and glitter. Lapetus is black on one side and white on the other.
Jupiter has 16 moons, four of which are very large. One of Jupiter’s moons is larger than Mercury and the other three are larger than our Moon. Charon, which orbits Pluto, is either a large moon or a small companion planet.
What are shooting stars?
Shooting stars, or meteors, are streaks of light that cross the night sky, although they can only be seen for one or two seconds. They are caused when a solid piece of rock called a meteoroid plunges through the Earth’s atmosphere, burning up due to air friction. When the rock enters the atmosphere it is known as a meteor. If, as rarely happens, a small fragment reaches the Earth, it is called a meteorite.
The Earth regularly passes through clouds of meteors orbiting the Sun. The best-known cloud, called the Perseids, reappears each year on August 12-13, sometimes producing spectacular meteor showers. There is also a regular meteor shower in December called the Geminids.
What is a comet?
Comets are often described as ‘dirty snowballs’. The solid centre, or nucleus, of a comet consists mostly of ice mixed with sooty material. The nucleus is quite small, and is usually only a few kilometres across.
Comets travel around the Sun in an elongated orbit. They plunge out into deep space beyond the farthest planet before diving back into the Solar System and passing close to the Sun. As the comet’s nucleus comes closer to the Sun it becomes smaller and may eventually break up into small fragments. Comets are thought to be as old as the Solar System itself.