AGILE highlights

AGILE is an ASI space mission in joint collaboration with INAF, INFN and CIFS, dedicated to the observation of the gamma-ray Universe. We present here an overview of AGILE highlights during the first 4 years of operations. The study of galactic gamma-ray transients with AGILE already brought very important results, such as the first confirmation of gamma-ray emission above 100 MeV from a colliding wind massive binary system in the eta -Carinae region, and of episodic transient gamma-ray flaring activity from Cygnus X-1 and Cygnus X-3 microquasars. The AGILE MCAL also detects surprisingly bright Terrestrial Gamma-ray Flashes (TGFs) in the Earth upper atmosphere up to 40 MeV and above, on millisecond timescales. The AGILE discovery of Crab Nebula variability above 100 MeV announced on September 2010 has astonished the scientific community. This finding was confirmed the next day by the NASA Fermi Observatory. Gamma-ray data provide evidence for particle acceleration mechanisms in nebular shock regions more efficient than previously expected from current theoretical models.