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Unformatted text preview: a) supernova explosion b) ionization fronts of hot, massive O & B star radiation c) collisions of giant molecular clouds d) spiral arms of galaxies Gravity starts contraction Gravity and thermal pressure (tug of war) Mass of molecular clouds are about 100 solar masses to be able to form stars Magnetic Fields, rotation, and turbulence can prevent or slow a stars contraction Molecular clouds are a place where stars form in multiples Bok Globules Herbig-Haro Objects T Tauri Stars Protostar Main Sequence Stars (fusion at core balances gravitational force) First Stars: contained only H and He no CO (that would cool collapsing molecular cloud) warmer environment that present epoch of clouds huge stars formed (greater than 30 solar masses) Gravitational Equilibrium (gravity inwards = pressure outwards) Stellar Mass: low limit: 0.08 M Sun upper limit: about 100 M Sun...
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- The Milky Way