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PX269 Galaxies Part 2: Our Galaxy, the Milky Way 2.1 Components and Structure PX269 Galaxies Slide 2 Wei-Hao Wang University of Hawaii The Milky Way Slide 3 Herschel, 1785 First map of Milky Way: Sun near centre Slide 4 Wei-Hao Wang University of Hawaii The Milky Way Slide 5 Kapteyn, 1922 Star counts with distance scale Slide 6 Globular cluster 47 Tuc, 2MASS Distribution of globular clusters suggests Sun not close to centre Slide 7 Distribution of globular clusters Shapley & Shapley, 1919 Slide 8 Wei-Hao Wang University of Hawaii Extinction in plane of Milky Way Slide 9 NGC 891, showing extinction Adam Block Slide 10 Slide 11 Vallee 2002 Slide 12 Slide 13 NGC 6744, Milky Way-like galaxy Capella Observatory Slide 14 Wei-Hao Wang University of Hawaii Extinction in plane of Milky Way Slide 15 NGC 891, showing dust extinction Adam Block Slide 16 Interstellar reddening Slide 17 Dust scattering Slide 18 Philip Perkins Pleiades open cluster Scattered light Slide 19 CFHT 2MASS NGC 891 OpticalInfra-red Slide 20 Wei-Hao Wang University of Hawaii Slide 21 COBE/DIRBE near infrared image of whole sky Slide 22 M 51 the Whirlpool Galaxy HII regions Slide 23 Wavelength (Angstroms) Flux Optical spectrum of an HII region Diaz et al 1987 Slide 24 Mike Fleenor HII regions: the Orion Nebula Slide 25 COBE/DIRBE near infrared image of whole sky Slide 26 HI map of whole sky Slide 27 21cm HI map of Milky Way Slide 28 NGC 6744, Milky Way-like galaxy Capella Observatory Slide 29 NGC 6744 in HI Ryder et al 1999 Slide 30 Molecular clouds Slide 31 Part 2: Our Galaxy, the Milky Way 2.2 Kinematics Slide 32 Galactic co-ordinates Carroll & Ostlie, 1996 Slide 33 Slide 34 Slide 35 HI map of whole sky Slide 36 21 cm line profile along one line of sight Carroll & Ostlie, 1996 Slide 37 Slide 38 21cm HI map of Milky Way Slide 39 Rotation curve of Milky Way Slide 40 A = rotation curve for centrally-concentrated mass distribution B = rotation curve for extended mass distribution Slide 41 Wei-Hao Wang University of Hawaii The Milky Way Slide 42 Gravitational microlensing method Slide 43 First detection of a gravitational microlensing event Alcock et al 1993