Will cover all material, but emphasis is on material covered since the last exam. The mass of a star determines how long it will live.
More massive stars evolve faster.
Molecular Clouds Stars form in giant clouds of gas and dust called molecular clouds. The large amount of gas and dust in the cloud shields the molecules from UV radiation from stars in our galaxy. The molecular cloud does not collapse into a single star. It fragments into many clumps. These clumps can further collapse to form stars.