ASTR 1102 Lecture : Lecture32
Document Summary
No - infrared images indicate many cooler stars between arms. Only 5% more stars in spiral arm than between. Not entirely - radio images indicate additional arcs that are not bright in visible light. They are only found near their birthplace. Inner stars have smaller orbits shorter rotation periods. Spiral arm should only last a few hundred million years. Jam persists even though cars continuously move through it. Spiral arm persists, though stars move through it. Stars, gas, dust are compressed closer together. Gas clouds pass through spiral arm from behind. Gas clouds in spiral arm turn into star formation region. Young star cluster emerges from front of spiral arm. Initially light dominated by most luminous, young, hot stars. As stars move ahead of spiral arm, hottest stars die off, leaving dimmer stars between spiral arms. We think our galactic bulge does have a bar. Close encounter can draw out spiral waves.
