Astronomy › Section T · Galaxies and quasars › Topic T.4
The extragalactic distance scale
Almost everything we want to know about a galaxy, from its size to its luminosity, depends on its distance. Astronomers measure those distances with a ladder of methods, each calibrated by the one below it.
In this topic
- Why galaxy distances are hard
- The ladder so far
- The tip of the red giant branch
- Worked example: a red-giant distance
- Type Ia supernovae
- Worked example: a supernova distance
- The Tully-Fisher relation
- Worked example: two spirals
- More methods, longer reach
- Common mistakes to avoid
- Key takeaways
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