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A truly dark sky has a surface brightness of 2 × 10 −4 cd m −2 or 21.8 mag arcsec −2. [9] [clarification needed] The peak surface brightness of the central region of the Orion Nebula is about 17 Mag/arcsec 2 (about 14 milli nits) and the outer bluish glow has a peak surface brightness of 21.3 Mag/arcsec 2 (about 0.27 millinits). [10]
The Tolman surface brightness test rules out the tired light explanation for the cosmological redshift. By the 1990s and on into the twenty-first century, a number of falsifying observations have shown that "tired light" hypotheses are not viable explanations for cosmological redshifts. [2]
The Tolman surface brightness test is one out of six cosmological tests that were conceived in the 1930s to check the viability of and compare new cosmological models. Tolman's test compares the surface brightness of galaxies as a function of their redshift (measured as z ).
(The S 10 unit is defined as the surface brightness of a star whose V-magnitude is 10 and whose light is smeared over one square degree, or 27.78 mag arcsec −2.) The total sky brightness in zenith is therefore ~220 S 10 or 21.9 mag/arcsec² in the V-band. Note that the contributions from Airglow and Zodiacal light vary with the time of year ...
Surface brightness fluctuation (SBF) is a secondary distance indicator used to estimate distances to galaxies. It is useful to 100 Mpc ( parsec ). The method measures the variance in a galaxy's light distribution arising from fluctuations in the numbers of and luminosities of individual stars per resolution element.
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. [1] In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, and relies on the context of the viewing environment (for example, see White's illusion).
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How is surface brightness any different than luminance? Seems they are not and the two articles should merged. Seems they are not and the two articles should merged. — TimL • talk 05:13, 27 January 2014 (UTC) [ reply ]