Absolute Magnitude

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Magnitude is a measure of the brightness of a star, planet, or other object in space. The scale is logarithmic and the brighter the object the lower the number.

Magnitude is usually one of two types:

  1. Apparent Magnitude (m) and...
  2. Absolute Magnitude (M). Absolute Magnitude is the brightness at 10 parsecs distance.

Description (Specifications)[edit]

Given the absolute magnitude and the distance to a star, the apparent magnitude can be calculated by: <math>m = M + 5((\log_{10}D)-1)</math> where D is the distance in Parsecs (must be adjusted for extra galactic objects). Thus Antares at M -5.28 as seen from Capital (distance of ~38 parsecs) would be:
<math>m = -5.28 + 5((\log_{10}38)-1)</math>
<math>m = -5.28 + 5(1.58-1)</math>
<math>m = -5.28 + 5(0.58)</math>
<math>m=-5.28 + 2.9</math>
<math>m=-2.38</math>

Absolute/Apparent Magnitude[edit]

Absolute/Apparent Magnitudes for comparison:

Absolute/Apparent Magnitude
Object Absolute Magnitude Apparent Magnitude (Terra) Apparent Magnitude (Capital)
Sun 4.83 −26.73 10.38
Moon (full) n/a −12.6 n/a
Visible during Daylight n/a −3.9 -3.9
Moon (new) n/a –2.5 n/a
Sirius Brightest Star 1.42 −1.47 6.97
Canopus 2nd Brightest star −5.53 -0.7 (-2.04) (0.73)
Vega 5th Brightest star 0.58 0.03 5.96
Antares 16th Brightest star −5.28 1.09 (0.83) -1.35 (-2.38)
Deneb 19th Brightest star −8.73 1.25 (-2.2) 0.96 (-3.09)
LBV 1806-20 −14.2 8.4 8.4
Quasar 3C 273 −26.7 12.8 12.8
  • Note the numbers in () above are for adjusted locations of stars on the maps.

History & Background (Dossier)[edit]

On ancient Terra the stars of the sky were divided into 6 magnitudes, with 1 being the brightest and 6 the faintest with each division being approximately 2 times difference, this was later revised so that a 1st magnitude star was 100 times brighter than a 6th magnitude star. First Polaris then Vega were taken to be the 0 point on the scale. So each step is the fifth root of 100 different (2.512).

Magnitude is not limited to the 0-6 scale, most primary stars will be highly negative (Sol from Terra is −26.73). The faintest magnitude visible with a human eye is 6.5. Binoculars give 9.5, and an 8m Ground Telescope can resolve to 27.

  • Apparent Magnitude: A measure of its brightness as seen by an observer on the ground, normalized to the value it would have in the absence of the atmosphere
  • Absolute Magnitude: The apparent magnitude, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction

References & Contributors (Sources)[edit]

This list of sources was used by the Traveller Wiki Editorial Team and individual contributors to compose this article. Copyrighted material is used under license from Far Future Enterprises or by permission of the author. The page history lists all of the contributions.