Lesson 4 of 6
The Sun, stars and galaxies
Goal: Describe our place in the universe.
The Sun is a star. It is one of billions of stars in our galaxy, and our galaxy is one of billions in the universe.
A planetThe Earth is one of eight planets that orbit the Sun.
The solar systemThe Sun and everything that orbits it.
A galaxyBillions of stars, with gas and dust, held together by gravity. Ours is called the Milky Way.
The universeEverything that exists. It holds billions of galaxies.
- A star gives out its own light. The Sun is the nearest star to us. Other stars look tiny because they are so far away.
- Planets and moons do not give out light. We see them because they reflect light from the Sun.
- Many stars have planets. A planet that orbits a star other than the Sun is called an exoplanet.
Why the Moon changes shape
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Key words in this lesson
Gravity A force that pulls any two objects towards each other
Orbit The path of a planet, moon or satellite around a larger body
Star A huge ball of hot gas that gives out its own light
Planet A large ball of rock or gas that orbits a star
Solar system The Sun and everything that orbits it
Galaxy A huge collection of stars, gas and dust, held together by gravity
Milky Way The galaxy that our solar system is in
Universe Everything that exists, including all the galaxies
Exoplanet A planet that orbits a star outside our solar system