Wiktionary
n. (context astronomy English) The intrinsic luminosity that a celestial body would have if viewed from a distance of 10 parsecs or 32.6 light years.
WordNet
n. (astronomy) the magnitude that a star would have if it were viewed from a distance of 10 parsecs (32.62 light years) from the earth
Wikipedia
Absolute magnitude is the measure of intrinsic brightness of a celestial object. It is the hypothetical apparent magnitude of an object at a standard distance of exactly 10 parsecs (32.6 light years) from the observer, assuming no astronomical extinction of starlight. This places the objects on a common basis and allows the true energy output of astronomical objects to be compared without the distortion introduced by distance. As with all astronomical magnitudes, the absolute magnitude can be specified for different wavelength intervals; for stars the most commonly quoted absolute magnitude is the absolute visual magnitude, which uses only the visual (V) band of the spectrum ( UBV system). Also commonly used is the absolute bolometric magnitude, which is the total luminosity expressed in magnitude units that takes into account energy radiated at all wavelengths, whether visible or not.
The brighter the celestial object the smaller its absolute magnitude. The magnitude scale extends downward through the positive numbers and into the negative numbers as brightness increases. A difference of 1.0 in absolute magnitude corresponds to a ratio of 2.512 ≈ 10 of absolute brightness. Therefore, a star of magnitude -2 is 100 (or 2.512) times brighter than a star of magnitude +3. The Milky Way, for example, has an absolute magnitude of about −20.5, so a quasar with an absolute magnitude of −25.5 is 100 times brighter than the Milky Way. If this particular quasar and the Milky Way could be seen side by side at the same distance of one parsec and the Milky Way's stars reduced to a single point, the quasar would be 5 magnitudes (or 100 times) brighter than the Milky Way. Similarly, Canopus has an absolute visual magnitude of about −5.5, whereas Ross 248 has an absolute visual magnitude of +14.8, for a difference of about 20 magnitudes, i.e. Canopus would be seen as about 20 magnitudes brighter; stated another way, Canopus emits more than 100 million (10) times more visual power than Ross 248.
Absolute Magnitude is a discontinued, semi-professional science fiction magazine started in 1993 under the name Harsh Mistress. However, in 1994 after only two issues the name was changed to Absolute Magnitude. In 2002 the name was changed again to Absolute Magnitude & Aboriginal Science Fiction when the publishers acquired the rights to Aboriginal Science Fiction. Absolute Magnitude was published by DNA Publications and edited by Warren Lapine. Although it was supposed to be a quarterly magazine its actual releases were irregular. After releasing twenty-one issues under the Absolute Magnitude title (plus two as Harsh Mistress), the magazine ceased publication in March 2006.
Absolute Magnitude was nominated for the 2002 Hugo Award for Best Semiprozine with Lapine noted as the editor.
Usage examples of "absolute magnitude".
At this distance the star, which had a mean absolute magnitude of plus one, was barely tolerable at the peak of its eight-day cycle.
We plot the star's absolute magnitude-that's its brightness on a standard scale-on the vertical line of the graph.
No visible internal energey sources, but Sentinel glows faintly with its own light (absolute magnitude +25) and is visible from every point of the Ryders-M system.
With an experimental skill rare at their age, the young men succeeded in making a complete study of the new phenomenon, established the conditions of symmetry necessary to its production in crystals, and stated its remarkably simple quantitative laws, as well as its absolute magnitude for certain crystals.
A last reading with the photocell gave me the apparent magnitude and a comparison with its absolute magnitude showed its distance.