Wobbling Stars

The radial-velocity method

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Stars wobble around the centre of mass they share with their planets.
• The wobble shows up as a periodic Doppler shift.
• Early discoveries favoured big, close-in planets: a selection effect.

Steps

1. Both bodies orbit
2. Watching the star wobble
3. The Sun’s wobble
4. Fit the wobble
5. How close in?
6. Balancing momenta
7. Hot Jupiters