Edwin Hubble Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time. Hubble discovered that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. He used the strong direct relationship between a classical Cepheid variable's luminosity and pulsation period (discovered in 1908 by Henrietta Swan Leavitt) for scaling galactic and extragalactic distances. Hubble provided evidence
Extragalactic background light 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 (SED) 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. The direct measurement of the EBL is a difficult task mainly due to the contribution of zodiacal light that is orders of magnitude higher than the EBL. Different groups have claimed the detection of the EBL in the optical and