WhereStarsFormpart2

WhereStarsFormpart2 - H 21 cm emission map (spin ip) H I...

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Ionized Interstellar Gas H II regions – ionized hydrogen gas clouds – Near massive, young stars (note the stars in the center of this picture) – ionized gas fluoresces • electrons recombine with protons, forming neutral H • emits (red) optical light -- If we see an HII region, we know that stars formed recently there.
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Where Do Stars form within Galaxies? Or, Where is the ISM in Galaxies? To answer this question, we need to first look at what our Galaxy looks like. Milky Way is spiral galaxy •Stars orbit center of Galaxy •Sun not at center –located 2/3 of way out –26,000 LY from center
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Major Components of Milky Way • Disk (and spiral arms) – 100,000 LY diam., 1000 LY thick – contains: young er stars • dust and gas (ISM) • active star formation • open clusters • Bulge (nucleus) – size ~3000 LY – contains old stars, old globular clusters • Halo (spherical) – extends ~50,000 LY – contains: old stars • globular clusters
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Where is the ISM in Galaxies?
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Unformatted text preview: H 21 cm emission map (spin ip) H I regions found in disk ~ 400 LY thick; 80,000 LY diam. IR cirrus maps Dust also conned to disk H II regions and Giant molecular clouds found only in spiral arms sites of new star formation GAS in galaxies almost always settles into a disk, because it can cool (get rid of energy) An External Galaxy (the Whirlpool) with spiral arms A region of the nearby Whirlpool galaxy. Dark patches are regions where light from stars is blocked by dust. Red is glowing hydrogen gas from newly born massive stars in star clusters. Galactic Recycling Blue light scattered more Red light scattered less Interstellar Reddening Why the sky is blue: Blue light (shorter wavelengths) is scattered more than red light (longer wavelengths). When we look at the sky, the blue light is coming from more directions than the red light....
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WhereStarsFormpart2 - H 21 cm emission map (spin ip) H I...

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