Our solar system is the Sun and everything that goes around it: eight planets, their moons, dwarf planets like Pluto, asteroids and comets.
Key idea
The Sun is a star, a huge ball of hot, glowing gas. The eight planets in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Gravity keeps them going around the Sun.
| Planet | One fact |
|---|---|
| Mercury | closest to the Sun; a year is only 88 days |
| Venus | the hottest planet, with thick clouds |
| Earth | the only planet known to have life |
| Mars | the red planet, with a giant volcano |
| Jupiter | the biggest planet, with a Great Red Spot |
| Saturn | bright, wide rings of ice and rock |
| Uranus | spins tipped on its side |
| Neptune | farthest; the windiest planet |
The first four are small and rocky. The outer four are giants made mostly of gas or ice. A sentence can help you remember the order: "My Very Eager Mother Just Served Us Noodles."
Why it works
The Sun looks bigger and brighter than other stars only because it is much closer. Its light takes about 8 minutes to reach us; light from the next nearest star takes over 4 years.
Worked example: Which planet?
Which planet is fourth from the Sun?
- Mercury 1, Venus 2, Earth 3, Mars 4.
Answer: Mars.
Common mistake
Thinking the Sun is not a star. It is an ordinary star, the closest one to us.
Try it at home
- On a long hallway or sidewalk, make a model with steps: Sun at 0, Mercury 1 step, Venus 2, Earth 2½, Mars 4, Jupiter 13, Saturn 24, Uranus 48, Neptune 75.
- How far apart are the outer planets compared with the inner ones?
Going further. Fly a spacecraft in the Orbit Lab; see The Solar System in Earth Science; read Sun, Moon, and Stars, and the young readers' path of Copernicus: On the Revolutions.