Planetary Nebulae Distance

Most Luminous Supergiants

The brightest supergiants in a given galaxy will have about the same absolute magnitudes, about -8 for red supergiants and about -9 for blue supergiants. These two types of supergiants can be seen out to about 50 Mly and 80 Mly respectively, compared to a maximum distance of about 20 Mly for Cepheid variables.

Most Luminous Globular Clusters

Beyond 80 million light years, even the brightest blue supergiants fade from view and one must turn to entire star clusters and nebulae for luminosity measurement. The brightest globular clusters have total luminosity of about magnitude -10 and can be seen out to 130 Mly.

Most Luminous H II Regions

The brightest H II regions have absolute magnitudes of about -12 and can be detected out to about 300 Mly, compared to about 130 Mly for the brightest globular clusters.

Distance from Supernovae

Beyond 300 Mly where even the brightest HII regions are indistinct, the only individual standard candles are supernovae which can reach a peak magnitude of -19. In theory, such a magnitude should be visible to 8 billion light years. However, supernovae types Ib, Ic and II show large brightness variations and there can be intervening matter.

However, the supernovae that are classified as Type 1a have been of great usefulness and are thought to provide a distance measurement uncertainty approaching 5% over vast distance ranges.