Measuring the distance to
galaxies
•Cepheids too faint to be standard candles in distant
galaxies
•But all Type Ia supernovae reach same maximum
brightness
•Cepheid + supernova in IC 4182 ® supernova as standard candle
•Supernovae enable distance measures from 1 Mpc
to 1 Gpc
•
For IC 4182, d = 5 Mpc
For supernova at maximum
brightness, we measure
m
= +8.6
\m-M = 8.6 –M =
28.5
\M = -19.9
& can be used to determine
distance modulus (m-M)
for other galaxies