1 Introduction 1
1.1 The stars 2
1.2 Our Milky Way 24
1.3 Other galaxies 32
1.4 Galaxies in the expanding Universe 40
1.5 The pregalactic era: a brief history of matter 44
2 Mapping our Milky Way 51
2.1 The solar neighborhood 51
2.2 The stars in the Galaxy 59
2.3 Galactic rotation 78
3 The orbits of the stars 95
3.1 Motion under gravity 96
3.2 Why the Galaxy isn't bumpy: two-body relaxation 107
3.3 Orbits of disk stars: epicycles 116
3.4 The collisionless Boltzmann equation 122
4 Our backyard: the Local Group 132
4.1 Satellites of the Milky Way 137
4.2 Spirals of the Local Group 150
4.3 How did the Local Group galaxies form? 154
4.4 Dwarf galaxies in the Local Group 164
4.5 Past and future of the Local Group 169
5 Spiral and SO galaxies 172
5.1 The distribution of starlight 173
5.2 Observing the gas 187
5.3 Gas motions and the masses of disk galaxies 194
Interlude: the sequence of disk galaxies 203
5.4 Spiral arms and galactic bars 205
5.5 Bulges and centers of disk galaxies 217
5.6 Groups: the homes of disk galaxies 221
6 Elliptical galaxies 231
6.1 Photometry 232
6.2 Motions of the stars 245
6.3 Stellar populations and gas 257
6.4 Dark matter and black holes 264
6.5 Galaxy clusters: the domain of elliptical galaxies 267
7 Large-scale distribution of galaxies 281
7.1 Observations of large-scale structure 282
7.2 Expansion of a homogeneous Universe 292
7.3 Growth of structure: peculiar motions 298
7.4 Growth of structure: clusters, walls, and voids 305
8 Active galactic nuclei and the early history of galaxies 313
8.1 Active galactic nuclei 314
8.2 Quasar absorption lines 337
8.3 The first galaxies 345
Appendix 361
A.Units and conversions 361
B.Bibliography 364
C.Hints for problems 366
Index 373