Forming Planetary Systems, Exoplanets and Life
How planetary systems are built from gas and dust, how astronomers find planets around other stars, and the great question of whether we are alone in the Galaxy.
Revise this, the fun way
Play it interactively, earn XP and build a streak, free.
Start revising freeWhat you'll cover
How planets are born 🪐
Around a young star, gas and dust slowly gather to build a **planetary system**. Gravity, tidal forces and countless collisions shape the planets, moons, rings and asteroid belts we see today. This module covers **how planetary systems form**, how astronomers find planets around other stars (**exoplanets**), and the biggest question of all: could there be **life** out there?
The forces at work 🌌
A few key ideas explain much of what happens in a planetary system:
What tidal forces can do 🌊
A moon strays too close to a giant planet and is pulled apart into a stream of debris. What is the name for the distance inside which this happens?
- The Roche Limit
- A Lagrangian point
- The Habitable Zone
- The escape velocity
The Roche Limit and rings 💍
The **Roche Limit** is the distance from a planet inside which its **tidal forces** are stronger than the gravity holding a smaller body together. A moon or comet that crosses it is torn apart, and the debris can spread into a **ring**. This is one reason the giant planets, such as Saturn, have ring systems.
Match each feature to its cause 🔗
- A planet's ring system
- Gaps in the asteroid belt
- Asteroids that share a planet's orbit
- A moon heated from the inside
- Tidal break-up of bodies within the Roche Limit
- Orbital resonance with a large planet
- Trapping at a stable Lagrangian point
- Tidal forces flexing and heating its interior
Round or lumpy? ⚪
Why are big worlds round but small ones potato-shaped?
How a planetary system forms 🌀
An interactive activity.
Finding other worlds 🔭
Planets orbiting other stars are called **exoplanets**. Three main methods find them:
What does life need? 🧬
Select the TWO conditions most important for life as we know it.
- Liquid water
- A source of energy
- A system of planetary rings
- At least ten moons
Complete the search 🧱
A planet orbiting another star is called an _____. The method that watches for a dip in starlight as a planet passes in front is the _____ method. The zone around a star where liquid _____ could exist is called the _____ Zone. The _____ equation estimates how many communicating civilisations there might be in our Galaxy.
Which worlds might host life? 🖍️
An interactive activity.
A Drake calculation 🔢
An interactive activity.
Is anyone out there? 🔀
An interactive activity.
Explain the search for life ✍️
An interactive activity.