•Parallax only works for nearby stars
•Spectroscopic “Parallax”
works somewhat further out
–Measure spectra and get Spectral Type and
Luminosity Class
–From those get Luminosity and then use
m-M to find distance
–Limited because need relatively bright
stars to get high resolution spectra
•Need another way to find M, then use m-M
to get distances
•
•Variable stars and the
Period-Luminosity relationship:
–Some stars vary in intrinsic brightness
with time
–The larger, more massive, and brighter stars vary more
slowly
•Like the relative pitch of a large vs.
small organ pipe