Where do the highest-energy cosmic rays originate?

One of the 523 cosmic-ray detectors in the Telescope Array, located in the Utah desert. [Credit: John Matthews, University of Utah]

One of the 523 cosmic-ray detectors in the Telescope Array, located in the Utah desert. She may not look like much, but she’s got it where it counts, kid. [Credit: John Matthews, University of Utah]

Light is only one way to see the Universe, but it’s the easiest. However, particle astrophysics — using particles like neutrinos or protons — can provide complementary information on some interesting objects in deep space…if we can only figure out where they’re coming from. That’s especially true for the highest-energy cosmic rays, which are protons from far-off sources carrying much more energy than we can achieve with accelerators like the Large Hadron Collider.

My latest for The Daily Beast is the story of how researchers have narrowed down the region on the sky where of most of the highest-energy cosmic rays come from, though not enough to say exactly where they’re originating.

Researchers at the creatively named Telescope Array in Utah showed that a significant fraction of the most energetic protons came from the same region—a “hotspot” about 80 times the width of the full Moon.

That’s not exactly a pinpoint, but it’s still a significant find. The hotspot is about six percent of the total sky, so if the sources of cosmic rays were evenly distributed throughout the universe, you’d expect roughly six percent of the highest energy particles to come from that region. Instead, the researchers found about 25 percent came from that region, indicating they may have a common source. [Read more…]



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