absolute magnitude

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absolute magnitude

astronomy

Also known as: M

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July 23, 2026

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In astronomy, absolute magnitude is a measure of a celestial body's intrinsic luminosity. It represents the apparent brightness an object would have if it were viewed from a standard distance of 10 parsecs, which is approximately 32.6 light-years. This differs from apparent magnitude, which is how bright an object appears from Earth.1234

The system for measuring magnitude was proposed by Norman Robert Pogson in 1850. In this system, a lower magnitude number indicates a brighter object. For instance, a star with a magnitude of 5.0 is 2.512 times brighter than a star with a magnitude of 6.0. Negative magnitudes are used for objects brighter than the standard reference points, such as the Sun, which has an apparent magnitude of -26.7.3

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star
Measuring starlight intensity
The absolute magnitude of a star is defined as the magnitude it would have if it were viewed at a standard distance of 10 parsecs (32.6 light-years). Since the apparent visual magnitude of the Sun is −26.75, its absolute magnitude corresponds to a diminution in brightness…
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The absolute magnitude of a star is defined as the magnitude it would have if it were viewed at a standard distance of 10 parsecs (32.6 light-years). Since the apparent visual magnitude of the Sun is −26.75, its absolute magnitude corresponds to a diminution in brightness…
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colour–magnitude diagram
…showing the relation between the absolute magnitudes (brightnesses) of stars and their colours, which are closely related to their temperatures and spectral types. It is similar to the Hertzsprung-Russell diagram except that the latter plots spectral types instead of colours.
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…showing the relation between the absolute magnitudes (brightnesses) of stars and their colours, which are closely related to their temperatures and spectral types. It is similar to the Hertzsprung-Russell diagram except that the latter plots spectral types instead of colours.
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Milky Way Galaxy
The stellar luminosity function
…show a conspicuous peak at absolute magnitude M_V = 0.5, and this is clearly due to the enrichment of stars at that magnitude from the horizontal branch of the cluster. The height of this peak in the data is related to the richness of the horizontal branch, which is in…
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…show a conspicuous peak at absolute magnitude M_V = 0.5, and this is clearly due to the enrichment of stars at that magnitude from the horizontal branch of the cluster. The height of this peak in the data is related to the richness of the horizontal branch, which is in…
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astronomy
Measuring observable stellar properties
By convention, the absolute magnitude (M) is defined as the magnitude that a star would appear to have if it were located at a standard distance of 10 parsecs. These quantities are related through the expression m − M = 5 log₁₀ r − 5, in which r…
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By convention, the absolute magnitude (M) is defined as the magnitude that a star would appear to have if it were located at a standard distance of 10 parsecs. These quantities are related through the expression m − M = 5 log₁₀ r − 5, in which r…
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Bertil Lindblad
…in studies to determine the absolute magnitude of distant stars from the stellar spectra (the characteristic individual wavelengths of light). Establishing his own spectral classification system, he used it to determine absolute magnitudes and, thence, the distance and transverse velocities of many distant stars.
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…in studies to determine the absolute magnitude of distant stars from the stellar spectra (the characteristic individual wavelengths of light). Establishing his own spectral classification system, he used it to determine absolute magnitudes and, thence, the distance and transverse velocities of many distant stars.
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