Description: Absolute magnitude is a measure with two different definitions. Both relate to how bright objects appear under a special set of conditions. This allows the intrinsic properties of objects at different distances to be compared. This is in contrast to apparent magnitude which is a measure of how bright an object appears from the location of the observer.

For objects outside the Solar System such as stars and galaxies, absolute magnitude is defined as the apparent magnitude an object would have when viewed from a standard distance of 10 parsecs, ignoring the effects of interstellar extinction. This standardized number allows different objects to be compared by how intrinsically bright they are.

Within the Solar System, absolute magnitude is defined as the apparent magnitude an object such as an asteroid would have if viewed at a distance of one astronomical unit from the observer, while the object is at a distance of one astronomical unit away from the Sun, and at opposition. Note that an object in the Solar System can never match these conditions when viewed from Earth but the definition removes factors that depend on the locations of the object and the observer to allow Solar System objects in different locations to be compared.

Related Terms:

• Apparent Magnitude
• Brightness
• Magnitude
• Parsec

Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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