Glossary |
Magnitude |
updated: 2023-10-27 |
Magnitude is a measure of brightness and being used for celestial objects. This measure was already used by Hipparchus to catalogue stars during the 2nd century BCE.
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Magnitude uses a logarithmic scale such that a star of magnitude 1 is exactly 100 time brighter than one of magnitude 6. Therefore the brightness variance between each step is 
.
Two different magnitudes definitions exist:
- apparent magnitude
- absolute magnitude
Apparent Magnitude (m)
Apparent magnitude is the brightness of an object as it appears in the night sky and is a really measure illuminance and can be measured in photometric units such as lux. Apparent magnitude depends on:
- the objects intrinsic luminosity
- its distance
- and the extinction reducing its brightness
Using this formula 
, you can easily calculate the difference in magnitude of some important celestial objects::
Magnitude examples:
- Sun:-26,832 mag - or ~ 55,564,831,284 times brighter then Vega
- Moon: up to -12,74 mag (full moon) - or ~128,233 times brighter then Vega
- ISS: up to -6 mag
- Venus (brightest value): -4.67 mag
- Sirius: -1.46 mag - or ~ 3,94 times brighter then Vega
- Mars: -2,91 mag
- Vega: 0,03 mag
- Polaris: 1.97 mag
- Andromeda Galaxy: 3.4 mag - or ~ 22.28 times dimmer then Vega
- Pluto: 13.9 mag - or ~ 353.183 times dimmer then Vega
- WJST apparent magniture (estimated): 23.7 mag - or ~2.937.649.652 times dimmer then Vega
Absolute Magnitude (M)
The absolute magnitude (M) describes the intrinsic luminosity emitted by an object and is defined to be equal to the apparent magnitude that the object would have if it were placed at a certain distance from Earth, 10 parsecs for stars.
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