3
Observations
of collapse
•Young
cluster “NGC 2264”
–Few
million years old
•High
mass stars have reached
main sequence
main sequence
•Lower
mass stars are still approaching main sequence
–T
Tauri stars
•Naming
of classes of stars: Usually named after first star in class: T Tauri
–Stars
with letters (RR Lyrae) are typically “variable” stars
•Earlier
stages hidden by dust
From our text: Horizons, by Sees
