1. Stellar and nebular spectra What we see from different angles. For a star, gas is its cooler atmosphere layers What’s going on? …. (Paint/demo)

2. Hydrogen Spectral Line Formation Transitions in Bohr atom model give rise to different groups Optical: Balmer (n=2) UV: Lyman (n=1) Ionization is transitions to/from infinity.

3. Balmer lines of Hydrogen Transitions are to/from n=2 level 3/2 is smallest change, thus lowest energy, thus ?? Color? What is the Balmer limit shown?

4. Doppler Effect on spectral lines Stationary source as shown at right emits wave fronts Moving source stretches wavelengths behind and shortens ahead

5. Doppler Equation Δλ / λ 0 = v / c Where C = speed of light V = radial velocity λ 0 = rest wavelength Δλ = change in wavelength or “Doppler shift” Doppler-shifted wavelength = λ + Δλ Shown here Δλ is negative (blueshift)

6. Use of Doppler Effect to find Planets Discover planets around other stars. More than a 200 now known.

7. Use Doppler to make a Radial Velocity Curve Notes: errors