Today in Astronomy 142: the Milky Way - Astro Pas Rochester

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What was missing from that last slide?• The Milky Way is a barred galaxy• Molecular ring outside the bar• The Milky Way is right now destroying a nearby diffusegalaxy called Sag A dwarf• In the halo there are stellar streams which are remnants oftidally disrupted dwarf galaxies• The outer part of the galaxy is probably flocculent ratherthan grand design• The outer part of the galaxy is warped and ringed?• The disk has two components (abundances and star counts):thin disk (few hundred pc) and athick disk (1kpc),The thick disk is older.Astronomy 142 10
Motions of stars in the Galaxy, and their use indetermining its mass distributionHow much does the Galaxy weigh?Stars move about in response to the gravitational potential ofthe rest of the stars in the galaxy.Their systematic motions (rotation) can be used simply withNewton’s Laws to measure masses.! This works even better with interstellar gas than withstars.Stars collide in-elastically very rarely, so their randommotions can be used with thermodynamics to measuremasses - the stars in this sense can be thought of as particlesin a gas.Let’s do some examples of the latter.Astronomy 142 11
Page 1 and 2: Today in Astronomy 142: the Milky W
Page 3 and 4: The Milky Way’scentral regions, i
Page 5 and 6: HI observations of the LMCKim et al
Page 7 and 8: More edge-on galaxiesNGC 4217 (HST
Page 9: Schematic structure of the Milky Wa
Page 13 and 14: Mass per unit area of the Galaxy’
Page 15 and 16: An easier way to estimate the force
Page 17 and 18: Dark matter I: the Galactic disk in
Page 19 and 20: Dark matter IIAstronomy 142 19
Page 21 and 22: Spiral structureAstronomy 142 21
Page 23 and 24: Density wave theory for spiral stru
Page 25 and 26: Spiral structureAstronomy 142 25
Page 27 and 28: X-shaped bulgeAstronomy 142 27

Today in Astronomy 142: the Milky Way - Astro Pas Rochester

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