Astronomy › Section L · Analysing starlight and the stellar census › Topic L.4
Using spectra to measure radius, composition, and motion
A star's spectrum is far more than a thermometer. The widths, strengths and positions of its lines reveal whether the star is a giant or a dwarf, what it is made of, how fast it moves towards or away from us, and how quickly it spins.
In this topic
- More than a thermometer
- Line widths reveal giant stars
- Luminosity classes
- Reading composition from line strengths
- Radial velocity from the Doppler effect
- Worked example: a star approaching us
- Proper motion
- From angles to speeds
- Worked example: the space velocity of Barnard's star
- Rotation broadens lines
- Common mistakes to avoid
- Key takeaways
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