Second, there were measurements of rotation taken for some of the nebulae. If a rotational movement could be measured, then they could not be that far away. Lastly, the distribution of the nebulae appears to be about the galactic plane, encouraging astronomers to believe that they are somehow associated with our galaxy. Because galaxies of all types seem to contain comparably old objects, it is believed that all galaxies are roughly the same age. If this is true, the Hubble tuning fork diagram cannot be an evolutionary sequence.
Stellar parallax allows astronomers to determine the distance to nearby objects.
Enough nearby Cepheid variables have had their distances found in this fashion to determine a period-luminosity relationship for the species. Luminous red and blue supergiants have had their absolute magnitudes inferred from their spectral classes and are usable as distance measurers out to 10 Mpc. Enough supernovae have been observed within 10 Mpc of the Sun, which includes the nearest galaxies, to allow astronomers to determine their absolute magnitudes at peak emission depending on the type. Supernovae are visible out to 100 Mpc, and so by measuring their apparent magnitudes, they may be used as distance markers. This method makes assumptions concerning the percent of the galaxy's mass that is luminous from what we know of our own galaxy and those nearby.