Dark Matter

Galaxies that spin too fast

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

• Galaxy rotation curves stay flat far beyond the visible disc.
• This implies huge halos of unseen dark matter.
• About 85% of the matter in the universe is dark.

Steps

1. Rotation curves
2. Fit the rotation curve
3. Mass that grows
4. Weighing the Milky Way
5. What could it be?
6. The Bullet Cluster