How bright an object would look if it were placed 10 parsecs (32.6 light-years) away. It measures its true luminosity, regardless of distance. The Sun, dazzling at −26.7, has an absolute magnitude of only +4.8; Rigel reaches about −7.
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Related terms
- Magnitude
The brightness scale of objects, running backwards: the smaller the number, the brighter the object. Five magnitudes make a factor of 100, one magnitude a factor of about 2.5. Vega is 0, Sirius −1.5, Venus up to −4.6; the eye reaches 6 under a dark sky.
- Parsec
The distance at which a star shows a parallax of one arcsecond when the Earth moves by one astronomical unit; its name comes from “parallax second”. One parsec is 3.26 light-years, or 206,265 astronomical units. Professional astronomers use it more than the light-year.
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