The planetary nebula Abell 39


Planetary Nebula Luminosity Functions For Distances to Galaxies

This page describes how planetary nebulae can be used to derive accurate distances to galaxies up to 20 Mpc away. Planetary Nebulae have very repeatable luminosity distributions, and this uniformity is the key to the technique.

The luminosity function for planetary nebulae in the nearby Andromeda Galaxy (M31). Notice that the function drops to zero very sharply at the bright (left) end of the distribution. This signature provides an indicator of the distance to a sample of nebulae.

For more information about planetary nebula luminosity functions (PNLF), see the pages listed below:

What is a PNLF?
How is the PNLF used to derive a distance?
What is the underlying theory?
Why does the PNLF method work in different kinds of galaxies?
What galaxies have been observed?
How accurate is the PNLF method?
How far can the PNLF method be used?
What are the latest results?
What do the critics say about the PNLF method?

So, What's the Hubble Constant?

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