10
Properties
of Galaxies
•Distance
–Use
Cepheid Variables for close objects
–Other
objects for which Absolute Magnitude is known:
•Supernova
•Planetary
nebula in certain emission lines
–Use
“Hubble Law” for more distant objects
•(Correlation
of distance with radial velocity)
•Diameter and Luminosity
–Obtain from angular size and magnitude, combined with
distance
•Mass
–Rotation
curves
–Velocity
dispersion
–90
to 99% of mass is
“dark matter”
“dark matter”
From our text: Horizons by Seeds