# Magnitude

Magnitude is a unit of measure for the brightness (or visibility) of stellar object.

## Description (Specifications)

Absolute magnitudes for stars generally range from -10 to +17.

There are two kinds of magnitude:

1. Apparent Magnitude (m) which measures the brightness of a stellar object from the point of view of the observer.
2. Absolute Magnitude (M) measures the brightness of a stellar object from 10 parsecs, or a planetary object from 1 Astronomical unit.

### Points of Reference

Some points of reference:

• Sol from Terra: -26.73
• Projects enough light to cast shadows: -5
• Faintest objects observable during the day with naked eye: −3.9
• Faintest stars visible in an urban neighborhood with naked eye: 3
• Faintest stars observable with naked eye under perfect conditions: 6.5
• Faintest objects visible with binoculars: 9.5

### Conversion

Given the absolute magnitude [itex]M\!\,[/itex], for objects within our galaxy you can also calculate the apparent magnitude [itex]m\!\,[/itex] from any distance [itex]D_L\!\,[/itex]:

[itex] m = M + 5 (\log_{10}{D_L} - 1)\!\,[/itex]

One can compute the absolute magnitude [itex]M\!\,[/itex] of an object given its apparent magnitude [itex]m\!\,[/itex] and luminosity distance [itex]D_L\!\,[/itex]:

[itex] M = m - 5 ((\log_{10}{D_L}) - 1)\!\,[/itex]

where [itex]D_L\!\,[/itex] is the star's luminosity distance in parsecs, which are (≈ 3.2616 light-years)

## History & Background (Dossier)

The original magnitude measurement was a scale of 1 to 6 to categorize the stars visible in the Terran skies. This was later formalized into a logarithmic scale, with the smaller numbers indicating brighter objects than larger ones. The scale is defined such that each 5 points magnitude is 100 times brighter (or dimmer). The scale also extends into the negative numbers, so for example magnitude -5 is 100 times brighter than magnitude 0.

## References & Contributors (Sources)

 This page uses content from Wikipedia. The original article was at Apparent_magnitude. The list of authors can be seen in the page history. The text of Wikipedia is available under the Commons Attribution-ShareAlike 3.0 Unported License.
 This page uses content from Wikipedia. The original article was at Absolute_magnitude. The list of authors can be seen in the page history. The text of Wikipedia is available under the Commons Attribution-ShareAlike 3.0 Unported License.