AST201H1 Study Guide - Midterm Guide: Helium Flash, Red Giant, Net Force

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST201H1
• Professor: Michael Reid

Document Summary

Cosmological redshift the expansion of the universe stretches out all the photons within it, shifting them to longer, redder wavelengths: tells us how much space has expanded during the time since light from the galaxy left. An objects lookback time is directly related to its redshift. Lookback time the difference between the current age of the universe and the age of the universe when the light left the object. Galaxies are moving away from one another; implies that galaxies must have been closer together in the past: the periods are very closely related to their luminosities: the longer the period, the more luminous the star. Obey a period-luminosity relationship: once we measure its period, we know its luminosity and can use the inverse square law for light to determine its distance. Spiral galaxies (milky way): disks are filled with cool gas and dust, combined with hotter ionized gas, and usually display spiral arms.