Scientists Prove Cosmic Rays Are Made of Protons

Jul 01, 2010 By Phillip F. Schewe
Cosmic rays, originating outside our Milky Way galaxy, slam into our atmosphere, where they set up a shower of secondary particles. Credit: NASA

Cosmic rays are made of protons, scientists found as they used a vast array of telescopes arranged across the Utah desert. Each telescope in the 67-unit arrangement sees the sky with a multifaceted eye. It’s no wonder they call it Fly’s Eye.

Scientists at the High Resolution Fly’s Eye detector, nicknamed HiRes, in the Army’s Dugway Proving Grounds in Utah, determined that the positively-charged components found in the center of each atom are what make up cosmic rays. Previously they had not been sure that the high-energy rays hadn’t been something heavier, such as the nucleus of an iron atom.

Cosmic rays, originating outside our galaxy, slam into our atmosphere, where they set up a shower of secondary particles. These particles cause nitrogen molecules in the air to glow slightly. The energy of the glow is recorded in sensitive photo-detectors attached to the telescopes. The particles made a conical pattern and deposited a characteristic energy spray in the detectors.

Cosmic rays have energies that can be much higher than anything produced by physicists. HiRes looks at the composition of with energies a million times greater than those generated on Earth, such as in the accelerator at the .

The HiRes detector can even determine the direction of the incoming cosmic ray. John Belz, a team member from the University of Utah, says that setting two sets of telescopes provides the stereo “seeing” needed to trace the cosmic ray’s incoming trajectory. The two arrays, each covering several acres, stand about 7 miles apart. The ray’s origin can be pinpointed to a region about as big as the full moon.

The experimenters logged data for several years between May 1997 and April 2006 and recently published their work in the journal .

Explore further: Sensitive detection method may help impede illicit nuclear trafficking

Provided by Inside Science News Service

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User comments : 8

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1 / 5 (2) Jul 02, 2010
"The ray’s origin can be pinpointed to a region about as big as the full moon"

Full? new/waxing/waning/crescent All the same size moon last I checked. Did you mean a cross section of space having the same area of our observable full moon?
1 / 5 (7) Jul 02, 2010
I can see that eventually we'll make the connection between cosmic radiation and cancer, and then we'll be tempted to move into underground dome cities or something. That or we'll figure out how to increase our shielding around cities.
2.6 / 5 (5) Jul 02, 2010
Na, the high energy collisions are going to create black holes and strangelets that will destroy the earth before we get the chance.
5 / 5 (2) Jul 02, 2010
OMG let's sign a petition to ban the universe's creation of cosmic rays!!
not rated yet Jul 03, 2010
"Cosmic rays, originating outside our Milky Way galaxy"

Oh really? Every last man jack of them? :-)
5 / 5 (1) Jul 03, 2010
Yes, what is the reasoning behind the extra-galactic origin?
not rated yet Jul 04, 2010
And how did they prove that the particles are protons? Presumably by something to do with the shape size and brightness of the shower produced.
not rated yet Jul 05, 2010
Reasoning for extra galactic nature, is that due to high energy the particles do not curve much in the galactic magnetic field, so their directional pattern should reflect the structure of the Milky Way if they came from it. Instead they come from all directions, so either they come from far off, or their directions have been scrambled by extremely large magnetic fields, or both.

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