Weighing Worlds

Mass plus size gives density

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Transits give radius, wobbles give mass, and together they give density.
• Density reveals composition: iron, rock, water or gas.
• Mini-Neptunes (between Earth and Neptune in size) are the most common planets found so far.

Steps

1. Earth’s density
2. Two methods together
3. The mass–radius diagram
4. Kepler-10b
5. Mini-Neptunes
6. A planet that floats