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Current theories assume that the low intensity of the stellar extragalacticbackground light (stellar EBL) is caused primarily by finite age of theUniverse because the finite age limits the number of photons pumped into thespace by galaxies and thus the sky is dark in the night. We oppose this opinionand show that two main factors are responsible for the extremely low intensityof the observed stellar EBL: (1) a low mean surface brightness of galaxies,which causes a low luminosity density in the local Universe, and (2) lightextinction due to absorption by galactic and intergalactic dust. Dust producesa partial opacity of galaxies and of the Universe. The galactic opacity reducesthe intensity of light from more distant background galaxies obscured byforeground galaxies. The effective extinction AV for light passing through agalaxy is 0.2 mag. This causes that distant background galaxies do notcontribute to the EBL significantly. In addition, light of distant galaxies isdimmed due to absorption by intergalactic dust. Even a minute intergalacticopacity of 1x10^(-2) mag per Gpc is high enough to produce significant effectson the EBL. The absorbed starlight heats up the galactic and intergalactic dustand is further re-radiated at the IR, FIR and micro-wave spectrum. Assumingstatic infinite universe with no galactic and intergalactic dust, the stellarEBL should be as high as the surface brightness of stars. However, if dust isconsidered, the predicted stellar EBL is about 290 nWm^(-2)sr^(-1), which isonly 5 times higher than the observed value. Hence, the presence of dust hashigher impact on the EBL than currently assumed. In the expanding universe, thecalculated value of the EBL is further decreased, because the obscurationeffect and intergalactic absorption become more pronounced at high redshiftswhen the matter was concentrated at smaller volume than at present.

Impact of galactic and intergalactic dust on the stellar EBL