ASTRON 1144- Midterm Exam Guide - Comprehensive Notes for the exam ( 44 pages long!)
12 Oct 2017
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How energy is transported is different depending on the mass of the star. 30 m sun protostar collapses in ~30,000 years. When core temperature > 10 million k: ignite 1st nuclear fusion in core. Low-mass protostars: take longer to become main-sequence stars: collapse is slower. Ionizes surrounding gas- hii region; blows away its cocoon. When core temperature > 10 million k: Below this, the core never gets hot enough to ignite h fusion; becomes a brown dwarf: Only about 100 are known, very faint. Maximum mass: 60-100 m sun ; core gets so hot: Ultimate limit is not precisely known; such stars are very rare. Leftovers: around low-mass stars, the remaining matter settles into a rotating disk: Dense mix of molecules, dust, ice stuff out of which planets might form. Matter can also be ejected along the poles of the protostar: Long, thin jets of matter; can be many parsecs long.
