Absolute Magnitude

A means of describing the intrinsic brightness of a star or other object: the effect of distance on the object's magnitude is eliminated by calculating its brightness as if it lay a fixed distance of ten parsecs (about 33 light years) from the Sun.

Because most stars lie further away than this, their absolute magnitude is typically greater than their apparent magnitude. Conversely, nearby stars tend to have less evident absolute magnitudes; if our own Sun lay at this distance from us, for example, it would scarcely be visible to the naked eye.

For objects within the Solar System, this definition cannot be used; other than the Sun itself, a distance of ten parsecs would simply render any such object invisible. Absolute magnitudes for such bodies are calculated as if the object lay at a point exactly one Astronomical Unit from both the Earth and the Sun.


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