Ten years of AGILE: the mission and scientific highlights

We review the main features and scientific results obtained during the first 10 years of the AGILE space Mission, a scientific program of the Italian Space Agency (ASI) focused on high-energy astrophysics. The Mission was proposed in 1997 for the ASI “Small Mission” Program and the instrument has been developed with the programmatic and technical support of INAF and INFN. The AGILE satellite was launched on April 23, 2007, from the Indian base in Sriharikota. We describe first the characteristics of the instrument and of the satellite. AGILE is a very innovative space Mission for its class, and is capable of reaching an optimal scientific performance for the study of astrophysical sources with detectors operating in the energy ranges 20–60 keV, 400 keV–100 MeV, 50 MeV–30 GeV. We review the main scientific achievements of the Mission with contributions to the study of the most energetic Galactic and extragalactic sources including accreting compact objects (neutron stars and black holes), pulsars, Supernova Remnants, Active Galactic Nuclei (AGN). AGILE made several important discoveries: a novel mechanism of particle acceleration operating in the Crab Nebula, the emission of transient gamma rays at the moment of launching of relativistic jets from Galactic compact sources, the first evidence of hadronic cosmic ray production from Galactic sources, the emission of very powerful gamma-ray flares from accreting super-massive black holes in AGN, sudden spectral transitions in gamma-ray bursts. Furthermore, AGILE is now providing unique contributions for the study of gravitational wave source counterparts and cosmic neutrino emitters. Also terrestrial applications are relevant for the science program: AGILE discovered gamma-ray emission above 20 MeV from Terrestrial gamma-ray flashes produced by powerful lighting and thunderstorms. This discovery has an important impact for environmental and atmospheric studies. In addition, particle resonance effects and time-dependent precipitations in the lower Earth magnetosphere can by addressed by AGILE studying the charged particles detected by the instrument. The AGILE satellite is operating nominally, and continues to observe the sky searching for the most energetic phenomena of our Universe.