mrpickles69
New member
...cluster requires that _______? a)we have telescopes powerful enough to allow us to identify the spectral types of main-sequence stars of many masses in the cluster
b)the cluster be near enough for us to measure the parallax of its stars
c)we use ultraviolet and X-ray telescopes
d)we have a well-calibrated period-luminosity relation for Cepheid variable stars
b)the cluster be near enough for us to measure the parallax of its stars
c)we use ultraviolet and X-ray telescopes
d)we have a well-calibrated period-luminosity relation for Cepheid variable stars