Distances deep into the Universe
You must use
nearby galaxies to calibrate distance indicators that can be seen across the Universe.
1)
brightest star (hypergiants), then HII region (star form.)
2)
largest spiral in cluster
3)
brightest galaxy in cluster
“Tully-Fisher”
relation:
Luminosity in red or infrared correlated with 21-cm
broadening
(number
of stars) (rotation
rate)
Hubble expansion: distance correlated with
redshift
