High-energy cosmic rays are extragalactic visitors from beyond our Milky Way

Now, for the first time, an international team of scientists using data from the Pierre Auger Observatory in Argentina have confirmed they are extragalactic visitors from beyond our Milky Way.

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Tau.Neutrino said:

High-energy cosmic rays are extragalactic visitors from beyond our Milky Way

Now, for the first time, an international team of scientists using data from the Pierre Auger Observatory in Argentina have confirmed they are extragalactic visitors from beyond our Milky Way.

more…

> “The magic thing is that we’ve actually seen — convincingly — something from another galaxy actually getting to us. I think that’s pretty amazing.”

Ah, nice.

The normal problem with cosmic ray astronomy is that the weak but huge magnetic fields of the Milky Way deflect the charged cosmic rays enough to make finding their origin impossible.

But the more energetic a cosmic ray is, the less it is deflected by the Milky Way. And it’s this that’s made the present work possible.

> it’s very rare for cosmic rays above 2 joules to reach Earth — there’s only about one per square kilometre per year — which means you need an observatory that covers a lot of ground to pick up a significant number of rays. The Pierre Auger Observatory is just that. The 3,000 square kilometre observatory, which sits at the base of the Andes in Argentina.

That makes sense. How powerful is 2 Joules compared to the LHC particles? “The record-smashing energy generated by the LHC’s collision events, therefore, only corresponds to 3.78 × 10 ^-7 J, a minuscule quantity of energy”. So 2 Joules is more than a million times as energetic as LHC particles.

> We haven’t solved that part of the mystery — we haven’t identified individual galaxies or sources at this stage, but this is a big step. The next step is homing in more precisely on those sources.

They meed a mathematical model of the Milky Way’s magnetic field, so they can subtract off its influence.