eagle nebula ngc 6611 6500 light years away stellar

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Unformatted text preview: y in the process • The expansive force released by fusion balances the contractive force of gravity, stabilizing the star as a discrete object in space ! ! ! ! Eagle Nebula - NGC 6611 - 6,500 light years away Stellar nursery - star-forming region Cloud is several hundred light-years across, and numerous protostars are visible within (in IR light) Our solar system would have begun in a similar nebula Hertzsprung-Russell diagram ! Solar luminosity v. log surface temperature • Shows a definite relationship among observable stars • Linear relation (main sequence) if H fusion is the dominant process • Red dwarfs => Blue giants • Sun (~6,000 K) Stellar Life Cycle ! ! ! ! Birth • Contraction begins fusion at a core temperature of ~20 million K • Early form of star is a “T-Tauri” star, with a strong solar wind Midlife • Fusion of H in stellar core, slow expansion of stellar diameter Senescence • Exhaustion of core H, fusion of H continues in expanding shell in mid-depth of star… significant stellar expansion • Star moves off of “main sequence” and becomes a Red Giant • At the red giant stage, core temperature increases while outer mantle of star cools by expansion • Eventually, star begins to fuse He to form C in core Death • Supernova - star detonates, may leave a pulsar or neutron star at its core, or a black hole (>3 solar masses) • White dwarf - lower mass stars dim to form a white dwarf star, which cools and fades as surface T decreases, fuel runs out Supernova remnant M1 (NGC 1952), the Crab Nebula Explosion observed 1054 A.D. (6,300 l.y. distant) Nearby Starforming Region: Orion Nebula (1,450 l.y.) • Lower inset: includes Trapezium, a group Lower of four massive stars. • In the larger Orion cloud complex: In ~2,300 young stars w/ planetary discs ~200 “stellar embryos” Nucleosynthesis ! ! ! Process forming elements heavier than He (or trace Li) Determined from nuclear fusion calculations, solar abundances of elements, meteorite and comet compositions Solar (cosmic) abundances of the elements • Obtained from spectrometric observation of the Sun’s corona (emission lines from io...
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This document was uploaded on 04/05/2014.

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