The diffuse extragalactic background light (EBL) is all the accumulated radiation in the Universe due to star formation processes, plus a contribution from active galactic nuclei (AGNs). This radiation covers the wavelength range between ~ 0.1-1000 microns (these are the ultraviolet, optical, and infrared regions of the electromagnetic spectrum). The EBL is part of the diffuse extragalactic background radiation (DEBRA), which by definition covers the overall electromagnetic spectrum. After the cosmic microwave background, the EBL produces the second-most energetic diffuse background, thus being essential for understanding the full energy balance of the universe.
The understanding of the EBL is also fundamental for extragalactic very-high-energy (VHE, 30 GeV-30 TeV) astronomy. VHE photons coming from cosmological distances are attenuated by pair production with EBL photons. This interaction is dependent on the spectral energy distribution of the EBL. Therefore, it is necessary to know the SED of the EBL in order to study intrinsic properties of the emission in the VHE sources.
Read more about Extragalactic Background Light: Observations, Empirical Modelings
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