1. Ay 123 Lecture I - Physical Properties 10  as = 10% distance @10kpc, 10  as/yr = 1km/s @20kpc ESA Gaia mission: a revolution in 3-D mapping of our Galaxy

2. wavelength flux Spectral energy distributions of bright stars can be used to derive effective temperatures Spectral Energy Distributions

3. Wavelength(  m) flux T eff Model atmospheres of varying [T eff, g] used to fit data

4. Stellar Spectral Energy Distributions Wavelength(Å) flux

5. Spectral Classification Diagnostic spectral lines act as independent measures of temperature in stellar atmosphere provided surface gravity is known

6. Stellar Spectra: Giants vs Dwarfs G K Stars are a 2-D sequence! Giants are slightly cooler than dwarfs of a similar spectral class with redder continua. This is because line strengths depend on T eff and g

7. Luminosity Classes

8. Overview of Stellar Evolution on H-R Diagram

9. Evolution During the Main Sequence Zero Age MS