This science story from earlier this week is pretty interesting, as is the way high energy ray direction was worked out:
To spot enough of the extremely rare highest energy cosmic rays, a detector array has to be huge, however. Auger consist of 1660 particle detectors covering 3000 square kilometers, an area nearly the size of Rhode Island, in the Pampa Amarilla in Argentina. Each detector is a tank holding 12,000 liters of ultrapure water that produces a flash of light when struck by particles. In addition, four stations of telescopes overlook the ground detectors.So this is what one cosmic ray detector looks like:
Spotting the sources of the most energetic rays was always going to be tough. Because they are electrically charged, cosmic rays swirl in the galaxy’s magnetic field. To point back toward their sources, they have to be so energetic that their paths do not curve too much. More common lower-energy cosmic rays—thought to emerge in the aftermath of supernova explosions in the Milky Way—curve so much in the galaxy’s magnetic field that they appear to come from all over the sky.
In spite of the difficulties, at first it seemed that Auger would find the sources of the higher-energy rays. It started taking data in 2004, and in 2007 Auger researchers announced that cosmic rays with energies above about 60 exa-electron volts (EeV) appeared to come from the fiery hearts of galaxies thought to contain supermassive black holes feeding on in-falling debris, so-called “active galactic nuclei.” However, that correlation has not held up as more data has come in. Moreover, Auger researchers had expected the highest energy cosmic rays to be light-weight protons, which bend less in magnetic fields. Instead, they have found that many of the rays consist of heavier nuclei, which curve more—making the job of figuring out their origin tougher.
Kind of pleasingly mundane looking for science technology.
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