Observing the Spectrum of M31
Below is the spectrum of M31. The locations of laboratory-measured lines of calcium K and H lines are indicated in red, and the laboratory wavelengths for them are given below. The corresponding calcium H and K lines from M31 can be seen in absorption. Look carefully in making your comparison. You may find it easier to print the image and estimate the Doppler shifted wavelengths using a ruler.
Possibly helpful quantities:
- Calcium K laboratory wavelength, λ0, Ca K = 3934 angstrom
- Calcium H laboratory wavelength, λ0, Ca H = 3969 angstrom
- Speed of light, c0 = 3×105 km/s