Intermediate
Do stars collide when galaxies merge?
The Milky Way disc contains roughly stars per cubic parsec, each of solar radius. Estimate the mean free path and collision timescale for a star moving at km/s, and comment on the Andromeda merger.
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Reading resources
Material that covers the physics behind this problem.
- An Introduction to Modern AstrophysicsCarroll & Ostlie
The standard reference for olympiad-level astrophysics. Chapters 1-3 cover the celestial sphere, orbits and the magnitude system.
Textbook - Ohio State Astronomy Lecture NotesOhio State University
Clear university-level notes on stars, galaxies and cosmology with derivations you can follow line by line.
Lecture notes