A New Light Boson from Cherenkov Telescopes Observations?
  Early indications by H.E.S.S. and the subsequent detection of blazar 3C279 by
MAGIC show that the Universe is more transparent to very-high-energy gamma rays
than previously thought. We demonstrate that this circumstance can be
reconciled with standard blazar emission models provided that photon
oscillations into a very light Axion-Like Particle occur in extragalactic
magnetic fields. A quantitative estimate of this effect indeed explains the
observed spectrum of 3C279. Our prediction can be tested by the satellite-borne
Fermi/LAT detector as well as by the ground-based Imaging Atmospheric Cherenkov
Telescopes H.E.S.S., MAGIC, CANGAROO III, VERITAS and by the Extensive Air
Shower arrays ARGO-YBJ and MILAGRO.
