Astronomy › Section S · The Milky Way › Topic S.5
Stellar populations and how the galaxy formed
The stars of the Milky Way are a fossil record. Their ages, their heavy-element content and the shapes of their orbits reveal how the galaxy was assembled: partly by the collapse of a great cloud of gas, and partly by swallowing smaller galaxies, a process still going on today.
In this topic
- Two kinds of stars
- Population I
- Population II
- Why older stars have fewer metals
- Worked example: reading the iron ratio
- The real world is messier
- Model one: a collapsing cloud
- Model two: built by mergers
- Worked example: when might Andromeda arrive?
- Common mistakes to avoid
- Key takeaways
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