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AGILE captures unprecedented gamma rays

The emission from collision wind of a binary star observed for the first time

It is a small satellite, but it continues to achieve big things. AGILE, the all-italian satellite for gamma ray astronomy, has captured one of the most powerful events in the Universe, anticipated for decades by theoretical studies but never observed before: the gamma ray emission from the collision winds in a binary stellar system, produced by the huge gas masses of two stars orbiting around each other.

The source is a super-star, Eta Carinae, the most massive star in our Galaxy. It is a blue hyper-giant, that will probably burst into a supernova in a few thousand years. Its mass is about a hundred times the Sun, and each week it eats up a mass equal to the Earth. This flux of matter collides with the one produced by its companion, generating a so-called “wind-wind collision”. The result is a gamma ray emission, up to now only speculated but never observed.

Now AGILE, using its sylicon detector GRID (Gamma Ray Imaging Detector), has provided the first experimental confirmation of this phaenomenon, to be published in The Astrophysical Journal Letters.