The solar system
Our Solar System (Separate Physics only)
Our has one star, the Sun. Orbiting the Sun are:
- Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
- , such as Pluto
- smaller objects such as asteroids and comets
Many planets have (moons) orbiting them, like our Moon. are machines we have launched into orbit.
The Sun formed about 4.6 billion years ago from a cloud of dust and gas pulled together by .
Remember
My Very Easy Method Just Speeds Up Naming: the planets in order from the Sun.
Key terms
Our galaxy (Separate Physics only)
Our Solar System is a tiny part of a called the . A galaxy is a huge collection of stars held together by gravity. The Milky Way contains billions of stars.
There are also billions of galaxies in the universe.
From smallest to largest: .
Key terms
How the Sun formed (Separate Physics only)
The Sun formed from a , a huge cloud of dust and gas, mainly hydrogen:
- pulled the dust and gas together.
- As it collapsed, it became hotter and denser, forming a .
- When the core was hot and dense enough, hydrogen nuclei began to into helium, releasing energy: the Sun began to shine.
The dust and gas left over around the young Sun came together to form the planets and the other objects that orbit it.
Key terms
What orbits what (Separate Physics only)
| Object | What it is | Example |
|---|---|---|
| Star | Gives out its own light, from fusion | The Sun |
| Planet | A large object orbiting a star | Earth |
| Dwarf planet | Orbits the Sun, but is too small to have cleared other objects from its orbit | Pluto |
| Natural satellite | A natural object orbiting a planet | The Moon |
| Artificial satellite | A machine launched into orbit | A weather satellite |
Everything in the Solar System is held in its orbit by .
Common mistake
The Moon is a natural satellite, not a planet: it orbits the Earth, not the Sun directly.