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Other magnitude systems calibrate by measuring energy directly, without a reference point, and these are called "absolute" reference systems. Current absolute reference systems include the AB magnitude system, in which the reference is a source with a constant flux density per unit frequency, [16] and the STMAG system, in which the reference ...
The apparent magnitude is the observed visible brightness from Earth which depends on the distance of the object. The absolute magnitude is the apparent magnitude at a distance of 10 pc (3.1 × 10 17 m), therefore the bolometric absolute magnitude is a logarithmic measure of the bolometric luminosity.
tech: power output of P-51 Mustang fighter aircraft 1.9 × 10 6 W astro: power per square meter potentially received by Earth at the peak of the Sun's red giant phase 2.0 × 10 6 W tech: peak power output of GE's standard wind turbine 2.4 × 10 6 W tech: peak power output of a Princess Coronation class steam locomotive (approx 3.3K EDHP on test ...
Factor ()Multiple Value Item 0 0 lux 0 lux Absolute darkness 10 −4: 100 microlux 100 microlux: Starlight overcast moonless night sky [1]: 140 microlux: Venus at brightest [1]: 200 microlux
Several measures of light are commonly known as intensity: . Radiant intensity, a radiometric quantity measured in watts per steradian (W/sr); Luminous intensity, a photometric quantity measured in lumens per steradian (lm/sr), or candela (cd)
Luminous intensity is the perceived power per unit solid angle. If a lamp has a 1 lumen bulb and the optics of the lamp are set up to focus the light evenly into a 1 steradian beam, then the beam would have a luminous intensity of 1 candela.
A-type star In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin.
Luminous energy: Q v [nb 3] lumen second: lm⋅s T⋅J: The lumen second is sometimes called the talbot. Luminous flux, luminous power Φ v [nb 3] lumen (= candela steradian) lm (= cd⋅sr) J: Luminous energy per unit time Luminous intensity: I v: candela (= lumen per steradian) cd (= lm/sr) J: Luminous flux per unit solid angle: Luminance: L v ...