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In contrast, the term brightness in astronomy is generally used to refer to an object's apparent brightness: that is, how bright an object appears to an observer. Apparent brightness depends on both the luminosity of the object and the distance between the object and observer, and also on any absorption of light along the path from object to ...
When appearing on light bulb packages, brightness means luminous flux, while in other contexts it means luminance. [5] Luminous flux is the total amount of light coming from a source, such as a lighting device. Luminance, the original meaning of brightness, is the amount of light per solid angle coming from an area, such as the sky.
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.
Galaxies (and other extended objects) are much larger than 10 parsecs; their light is radiated over an extended patch of sky, and their overall brightness cannot be directly observed from relatively short distances, but the same convention is used. A galaxy's magnitude is defined by measuring all the light radiated over the entire object ...
A difference of 1.0 in magnitude corresponds to the ... What is the ratio in brightness between the Sun and the ... (luminosity distance of 2.4 billion light-years ...
The difference between brightness and lightness is that the brightness is the intensity of the object independent of the light source. Lightness is the brightness of the object in respect to the light reflecting on it. This is important because the Helmholtz–Kohlrausch effect is a measure of the ratio between the two. [3]
The frequency of light used in the definition corresponds to a wavelength in a vacuum of 555 nm, which is near the peak of the eye's response to light. If the 1 candela source emitted uniformly in all directions, the total radiant flux would be about 18.40 mW , since there are 4 π steradians in a sphere.
In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on its surface luminosity density, i.e., its luminosity emitted per unit surface area.