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Resolution B2 defines an absolute bolometric magnitude scale where M bol = 0 corresponds to luminosity L 0 = 3.0128 × 10 28 W, with the zero point luminosity L 0 set such that the Sun (with nominal luminosity 3.828 × 10 26 W) corresponds to absolute bolometric magnitude M bol,⊙ = 4.74.
Because the magnitude is logarithmic, calculating surface brightness cannot be done by simple division of magnitude by area. Instead, for a source with a total or integrated magnitude m extending over a visual area of A square arcseconds, the surface brightness S is given by S = m + 2.5 ⋅ log 10 A . {\displaystyle S=m+2.5\cdot \log _{10}A.}
Therefore, the absolute magnitude can be calculated from a luminosity in watts: = + where L 0 is the zero point luminosity 3.0128 × 10 28 W and the luminosity in watts can be calculated from an absolute magnitude (although absolute magnitudes are often not measured relative to an absolute flux): L ∗ = L 0 × 10 − 0.4 M b o l ...
In astronomy, a phase curve describes the brightness of a reflecting body as a function of its phase angle (the arc subtended by the observer and the Sun as measured at the body). The brightness usually refers the object's absolute magnitude, which, in turn, is its apparent magnitude at a distance of one astronomical unit from the Earth and Sun.
The object's actual luminosity is determined using the inverse-square law and the proportions of the object's apparent distance and luminosity distance. Another way to express the luminosity distance is through the flux-luminosity relationship, = where F is flux (W·m −2), and L is luminosity (W). From this the luminosity distance (in meters ...
Absolute magnitude, which measures the luminosity of an object (or reflected light for non-luminous objects like asteroids); it is the object's apparent magnitude as seen from a specific distance, conventionally 10 parsecs (32.6 light years). The difference between these concepts can be seen by comparing two stars.
If the star lies on the main sequence, as determined by its luminosity class, the spectral type of the star provides a good estimate of the star's absolute magnitude. Knowing the apparent magnitude (m) and absolute magnitude (M) of the star, one can calculate the distance (d, in parsecs) of the star using m − M = 5 log ( d / 10 ...
Luminous flux per unit solid angle: Luminance: L v: candela per square metre: cd/m 2 (= lm/(sr⋅m 2)) L −2 ⋅J: Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit. Illuminance: E v: lux (= lumen per square metre) lx (= lm/m 2) L −2 ⋅J: Luminous flux incident on a ...