The Earth is one of eight planets orbiting the Sun – down from nine in 2006 due to the relegation of Pluto to a new status of dwarf planet. Some can be among the brightest objects in the sky and their changing appearance makes them fascinating to watch for stargazers.
You can see most of the planets with just your eyes alone – although not usually on the same night! Even the most distant, Uranus and Neptune, are bright enough to be spotted with binoculars if you know just where to look.
The brighter planets can be told apart from the stars because they don’t tend to twinkle as much. Starlight can appear to flicker noticeably because they are so far away that they are like points in the sky, distorted by our atmosphere. Planets are closer and so shine as tiny disks, even if they don’t look like disks to the unaided eye. This fact makes them less prone to twinkling!
Mercury and Venus are called inferior planets – but this doesn’t mean there is anything wrong with them. It is simply a term to tell us that they lie closer to the Sun than our Earth is and so they orbit within our own orbit. The planets beyond Earth – Mars, Jupiter, Saturn, Uranus and Neptune – are known as superior planets to denote that they are outside out own orbit.
Because of their position relative to Earth, Mercury and Venus stay fairly close to the Sun in the sky and so are visible either early in the morning before sunrise or in the evening after sunset. You won’t see them shining at midnight, unlike the outer planets which might be visible at any time of night depending on where they lie in their orbits.
Mercury, Venus, Earth (of course!) and Mars are rocky planets. Jupiter and Saturn are giant gasballs, and Uranus and Neptune are also giants but more icy in nature.