PHYS 182 Lecture Notes - Lecture 6: Parsec, Before Present, Recessional Velocity

• School: McGill University
• Department: Physics
• Course: PHYS 182
• Professor: David Hanna

Document Summary

All stars in the same cluster are the same distance to us. All clusters that are further are moved by the factor of the distance they are. See a fading on main sequence relative to distance 2. Standard candle shows that based on brightness of main sequence, we know its relative distance. Variable stars get bigger and smaller and pulse in and out. Periodic build up of pressure that is released and then build up. Measure distance to an individual star even in distant galaxies. When they enter instability region they pulsate. Calibration needs to be done with close cepheids. Plot average luminosity as a function of period. Stars with a longer period are much more luminous. You need variables stars that you can measure the actual luminosity. Need to use a measurement that you know (main sequence of star cluster, stellar parallax) You can use this information to know about a further variables stars.