The Sun, planets, dwarf planets and moons, natural and artificial satellites, how the solar system sits in the Milky Way, and huge distances in standard form and light-years.
What you will learn
- Name the bodies in the solar system and say what orbits what
- Put moons, planets, stars, galaxies and the universe in order of size
- Write space distances in standard form and convert light-years to metres
What orbits what
Our solar system is one star, the Sun, and everything that orbits it.
- Planets: eight of them, from Mercury out to Neptune, all orbiting the Sun.
- Dwarf planets: smaller bodies such as Pluto and Ceres that also orbit the Sun. A dwarf planet is nearly round but has not cleared other objects out of its orbit.
- Moons: natural satellites that orbit planets. The Earth has one; Jupiter and Saturn have dozens.
- Artificial satellites: made and launched by people, such as the International Space Station, weather and GPS satellites.
A satellite is anything that orbits a larger body. Gravity keeps every one of these orbits going.
The solar system formed from a nebula, a cloud of dust and gas pulled together by gravity. Most of it became the Sun; the rest formed the planets.
The rest of this lesson and its 8 practice questions are locked.
In this lesson
- What orbits what
- From the Moon to the universe
- Big numbers in standard form
- Try it: Your first conversion
8 practice questions, marked as you go; about 20 minutes in all.
Key terms
Solar system, Satellite, Nebula, Galaxy
In this unit: Space physics
The solar system and the Milky Way, the life cycle of a star, orbits and orbital speed, red-shift and the expanding universe, and what is still unknown.