Which of the following is an actual observation that falsifies (is inconsistent with) the theory that the Milky Way galaxy originated from the collapse of a spherical gas cloud that flattened into a disk?
a. We observe fewer white dwarf stars in the galactic disk than there should be for an 11-billion year old galactic disk.
b. The globular cluster stars in the galaxy halo are all old.
c. The metallicity of globular cluster stars is about one tenth the Sun's value.
d. Nonsense - all of the above observations are consistent with the standard collapse-from-a-cloud theory.
Which of the following is a correct list of distance indicators (standard candles) used by astronomers?
a. emission and reflection nebulae in molecular clouds; nova explosions on white dwarfs; main-sequence stars
b. white dwarf stars; Cepheid variables; black hole binary systems; massive star supernovae
c. lyra and cepheid variable stars; white-dwarf supernovae
d. emission by super-massive black holes located at the center of nearly every large galaxy; spinning spiral galaxies|||I think that is correct.
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