When teaching: Out with magnitudes, in with monochromatic luminosities!

TL;DR

This paper advocates replacing magnitudes with monochromatic luminosities in teaching and research to improve clarity and consistency in astronomy, supported by examples and conversion formulas.

Contribution

It introduces a clear argument and practical methods for transitioning from magnitudes to monochromatic luminosities in astronomy education and research.

Findings

Enhanced transparency in teaching concepts

Simplified conversion between systems

Potential for standardizing research communication

Abstract

The goal of this document is to illustrate that teaching the concepts of magnitudes is a needless complication in introductory astronomy courses, and that use of monochromatic luminosities, rather than arbitrarily defined magnitudes, leads to a large gain in transparency. This illustration is done through three examples: the Hertzsprung-Russell diagram, the cosmic distance ladder, and interstellar reddening. I provide conversion equations from the magnitude-based to the luminosity-based system; a brief discussion; and a reference to sample lecture notes. I suggest that we, astronomers in the 21st century, abolish magnitudes and instead use (apparent) monochromatic luminosities in non-specialist teaching. Given the large gain in transparency I further propose that we seriously consider using (apparent) monochromatic luminosities also in research papers, bringing optical astronomy in line with astronomy at other wavelengths. Comments are welcome.