Pulsars are known to power winds of relativistic particles that can produce
bright nebulae by interacting with the surrounding medium. These pulsar wind
nebulae (PWNe) are observed in the radio, optical, x-rays and, in some cases,
also at TeV energies, but the lack of information in the gamma-ray band
prevents from drawing a comprehensive multiwavelength picture of their
phenomenology and emission mechanisms. Using data from the AGILE satellite, we
detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV.
This result constrains the particle population responsible for the GeV
emission, probing multivavelength PWN models, and establishes a class of
gamma-ray emitters that could account for a fraction of the unidentified
Galactic gamma-ray sources.Comment: Accepted by Science; first published online on December 31, 2009 in
Science Express. Science article and Supporting Online Material are available
at http://www.sciencemag.or