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Abstract:
The discovery of several distant TeV blazars (redshift up to z~0.2 and possibly z~0.5) with the new generation Cherenkov telescopes HESS and MAGIC enables to set strong limits on the extragalactic background light (EBL) in the near to mid-infrared region. These upper limits are only a factor of two to three higher than the lower limits derived from source counts and several theoretical models could already be excluded. Such a low level of the EBL implies that the universe is much more transparent to VHE gamma-rays than previously anticipated. Here we summarize the recent results and discuss future prospects.
