Astronomy › Section E · Radiation and spectra › Topic E.6
The Doppler effect
Spectral lines tell us not only what a star is made of but also how fast it is moving towards or away from us. A tiny shift in where the lines fall is enough to weigh binary stars, spin galaxies and find planets around other suns.
In this topic
- A complication that became a tool
- Motion squeezes and stretches waves
- Hearing it with sound
- Blueshift, redshift and radial velocity
- The Doppler formula
- Worked example: a receding star
- Worked example: predicting a shift
- Lines, not colours
- What Doppler shifts reveal
- Common mistakes to avoid
- Key takeaways
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