Unit 25
The Solar System.
Our neighbourhood: the Sun and its sunspots, the planets, comets and asteroids, and planets of other stars.
Before this unit
The unit, lesson by lesson
Lessons
4 lessons · 30 practice questions · about 2 hours
The Sun
Our nearest star from the inside: its layers from the core to the surface, the sunspots that come and go in an 11-year cycle, and the magnetic field that flips and makes them.
The Solar System
Eight planets round one star: how far apart they really are, why a distant planet’s year is so long, and why the far planets are also slow.
Comets and asteroids
A long, thin orbit round the Sun: how long one lap takes, why the comet races near the Sun and crawls far from it, and why its tail always points away from the Sun.
Planets round other stars
How to find a planet you cannot see: the shadow it casts on its star’s light. How deep the dip is, how often it comes back, and why the orbit has to be seen almost edge-on.