The Solar System — Astronomy, 7–10 years
The Sun and the objects held in its neighbourhood make a family called the Solar System. The planets travel around the Sun, but they are not little stars.
A family around the Sun
The Solar System includes the Sun, eight planets, their moons, and many smaller objects such as asteroids and comets. The Sun is a star, much closer to us than the other stars we see. Its gravity keeps most of this family travelling around it.
What belongs together?
At first, the bright points in the sky seemed like one flat picture. Careful observations showed that some points wander against the background stars, while others stay together around the Sun. Grouping these objects solves the problem of describing our local space without treating every light as the same kind of thing.
Sorting space objects
Take three examples: the Sun, Earth, and the Moon. The Sun makes its own light, so it is a star. Earth travels around the Sun, so it is a planet. The Moon travels around Earth, so it is a natural satellite. All three belong to the Solar System, but they have different roles.
Planets are not stars
It is easy to call a bright planet a star because both look like points in the night sky. The important difference is that a star makes its own light and heat, while a planet reflects light from a star. A planet can look bright without glowing like the Sun.
Finding our place
The Solar System model helps spacecraft designers choose routes to the Moon, Mars, and beyond. It also helps observers tell a planet from a star by checking how its position changes over time. Understanding the system gives us a map of our nearby cosmic neighbourhood.
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