AST201H5 Lecture Notes - Lecture 3: Doppler Effect, Solar Mass
Document Summary
Milky way = band of faint light circling the whole sky. Faint light = combined light of very many faint stars -> milky way is a huge disk of stars, and the sun is in this disk. First attempt to measure the milky way used counting stars in different directions. Disk"s diameter is about 16,000 ly, thickness is about 1000 ly, sun is near the disk"s centre. Problem: space contains a thin distribution of dust that limits our view -> Milky way is much larger than we see. Avoid the dust by observing objects that are not in the band of the milky. Use globular star clusters: mostly above/below the milky way band, each cluster has a million stars -> very bright -> visible at great distances. Find mostly located in one direction in the sky. Center of concentration is 27,000 ly away.
