Distance Measurements to Other Galaxies (I)
a)Cepheid method: Using
period – Luminosity relation for classical Cepheids:
Measure
Cepheid’s period ® Find its luminosity ® Compare to apparent magnitude ® Find its distance
b) Type Ia supernovae
(collapse of an accreting white dwarf in a binary system):
Type Ia supernovae have
well known standard luminosities ® Compare to apparent magnitudes ® Find its distances
Both are “Standard-candle” methods:
Know absolute magnitude
(luminosity) ® compare to apparent magnitude ® find distance.
