- Gamma Rays are rays of high energy light, electromagnetic radiation. They contain energies of greater than 3,000,000 electron volts. Their frequency of oscillation is very high, greater than 30,000,000,000,000,000,000,000 cycles per second ( 10^22), and their wavelengths are very short, less than 0.00001 nanometers. ( 10^-14 meters). This temperature translates to 290,000,000,000 degrees Kelvin, ( T = 0.0029 / wavelength). Energy = Planck’s Constant of Action * frequency = 6.63*10^-34 * frequency in Joules. ( E = h*f)
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- Cosmic Rays are not rays at all, they are particles. High speed particles that carry Kinetic Energy = ½ * mass * velocity^2. These particles are the charged particles of atoms, nuclei and electrons. They were discovered in 1912 as tiny bits of matter traveling in the atmosphere at nearly the speed of light. Their tracks were seen in cloud chambers. They were discovered to be electrically charged because they were deflected with a magnetic field, much like a cathode ray tube operates a television.
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- Most Cosmic Rays pass through the Earth without touching anything. But, some can encounter atoms, some of these enter the human body causing mutations in tissue. Some can hit a computer chip and cause errors in computer memories. Some enter a telescope and cause an unwanted streak across a CCD image.
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- When Cosmic Rays hit air molecules they create a shower of billions of electrons, muons, and other fundamental particles, positrons, and pions. This is much the same as what happens in a particle accelerator.
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- High energy Cosmic Rays can carry 10^20 electron volts of energy. That is 10,000,000 times greater that can be created in a particle accelerator, the Large Hadron Collider at CERN, Switzerland. This energy level from a small particle is equivalent to a tennis ball traveling 53 miles per hour.
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- High energy Cosmic Rays are not common, striking a square mile area every 39 years. Of course the Earth has a lot of square miles but where to put an observatory to catch these rare events?
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- The high deserts of the Andes Mountains in Argentina, bordering Chile. The telescope is a grid of water tanks spread over 1,200 square miles. 1,600 water tanks each holding 3,170 gallons of water. When a high speed cosmic ray enters the water it is traveling faster than the speed of light in water. This creates an electromagnetic shock wave and a flash of blue light.
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- All of the water tanks contain light detectors that can record the Cosmic Ray’s arrival within nanoseconds.
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- In addition to the water thanks there are 4 buildings designed to detect fluorescence nitrogen. High energy nitrogen atoms emit an ultraviolet glow.
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- These “telescope” detect several thousand Cosmic Rays and one high energy ray every 60 days. By comparing the timing and the trajectory angles astronomers can triangulate the source within 3.1 square degrees. ( The Full Moon is 0.5 square degrees.) Low energy Cosmic Rays get deflected by the Earth’s magnetic field but the high energy Cosmic Rays tend to travel closer to a straight line.
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- Theory is that these high energy Cosmic Rays originate in super massive Blackholes at the center of most galaxies. In falling material spirals around the Blackhole creating an accretion disk. The rotating plasma of charged particles create a friction generating heat to millions of degrees. Jets of this material shoot out the poles.
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- Galaxy M87 is being studied to confirm this theory, but, we need more data. Most Cosmic Rays are protons but some may even be iron nuclei. Heavier nuclei could contain much higher kinetic energy, but, the math still does not explain these exceedingly high energies. The mystery remains.
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- The average energy Cosmic Rays that are mostly protons are now confirmed as originating in supernovae explosions. The evidence comes from 4 years of data accumulated by the Fermi Gamma Ray telescope.
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- Supernovae shockwaves accelerate protons, the nuclei of hydrogen atoms, to near light speed. When these nuclei collide with other atoms they emit a unique fingerprint of Gamma Rays. 90% of the Cosmic Rays entering Earth’s atmosphere are these protons.
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- This has been a difficult study because protons are positively charged particles and when they enter Earth’s magnetic field their trajectories are deflected with a right angle force. This makes it almost impossible to determine which direction they originated from. The proton collisions near the supernova source have provided the indirect evidence that this was the source. Gamma Rays travel in a straight line as high energy light that is unaffected by magnetic fields.
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- Looking in the plane of our Milky Way astronomers have detected over 500 sources of Gamma Rays exceeding 10 billion electron volts. When a Blackhole accretion disk pole and jets are aimed directly at us we see the bright beam of Gamma Ray light.
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- These Gamma rays travel across billions of lightyears to reach us. They pass through and collide with the extragalactic background light creating pairs of matter - anti-matter, electrons and positrons. The Gamma Ray signal disappears when the pair production of matter-anti-matter happens.
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- The farthest galaxies are missing their high energy Gamma Rays ( >25 GeV) due to this attenuation process. By measuring this attenuation astronomers are able to calculate the average density of stars in the cosmos. There are an average of 1.4 stars fro every 100 billion cubic lightyears. They have concluded the star formation reached its peak when the Universe was 3 billion years old. Star formation has been on the decline the last 10 billion years.
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- There are still many mysteries to solve with Gamma Rays and Cosmic Rays. Astronauts report seing flashhesof light caused by Cosmic Rays entering the brain. We need to learn more about the health affects on space travelers.
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- The Crab Nebula has flashes of Gamma Rays that grow to 30 times normal and last for several days. The flashes exceed 100 million electron volts. This may have something to do with a massive magnetic field suddenly switching polarity. Mysteries remain. Announcement will be made shortly , stay tuned.
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RSVP, please reply with a number to rate this review: #1- learned something new. #2 - Didn’t read it. #3- very interesting. #4- Send another review #___ from the index. #5- Keep em coming. #6- I forwarded copies to some friends. #7- Don‘t send me these anymore! #8- I am forwarding you some questions? Index is available with email upon request. Some reviews are at http://jdetrick.blogspot.com Please send feedback, corrections, or recommended improvements to: jamesdetrick@comcast.net. ---- “Jim Detrick” -- www.facebook.com, -- www.twitter.com, -- 707-536-3272 Sunday, February 24, 2013
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