Ultra High-Energy Cosmic Rays 超高能宇宙線

Documentary: Global Village, Pampa Scientists.

On the Argentinian Pampas Antoine Le Tessier Selvant, the director of the CNRS法國國家科學研究中心, the national centre for scientific research, has been installing research tanks since the year 2000.  There are now 1600 of them in place and they constitute the world’s biggest ultra-high-energy cosmic ray observatory.  We visit the local residents to see what they make of the strange structures, and the scientists who look after this remarkable facility.

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Malargue was chosen by the National Centre for Scientific Research as a location to build the world’s biggest ultra-high-energy cosmic ray observatory.

every second, 200 cosmic rays hit every square metre of the planet.  Among these, a few have enough energy to lift a one-kilogram object a metre high.

The Pierre Auger Observatory was built to study these extremely rare ultra-high-energy cosmic rays, to understand their nature and origin.

http://en.wikipedia.org/wiki/Pierre_Auger_Observatory

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Along with the tanks placed one and a half kilometres apart, a network of 24 telescopes is used.  The role is observe particle showers produced by the cosmic rays, when they penetrate the earth’s atmosphere.

the water Cherkov detector (small water basins, 1.2 m deep; called "tanks")

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The small blue dots represent the tanks installed in the Pampas, and when an event occurs, it’s represented in yellow or green on this drawing.

For example, here we see the footprint of a cosmic ray, which was recorded at more than twenty stations. extending across 20 kilometres. And here we see that this cosmic ray has an energy of 2 followed by 19 zeros electron volts. It would heat one gram of water about one degree, not even enough to make a cup of coffee.

With telescopes tracking down tiny light sources and electron volts with endless zeros, this research has found new impetus in Argentina. 

http://en.wikipedia.org/wiki/Cosmic_ray

http://imagine.gsfc.nasa.gov/docs/science/know_l1/cosmic_rays.html

cosmic rays : are mostly pieces of atoms 原子:protons 質子, electrons 電子, and atomic nuclei 原子核which have had all of the surrounding electrons stripped during their high-speed (almost the speed of light) passage through the Galaxy

In astroparticle physics, an ultra-high-energy cosmic ray (UHECR) is a cosmic ray particle with a kinetic energy 動能 greater than 1018 eV, far beyond both its rest mass and energies typical of other cosmic ray particles.

An Extreme-energy cosmic ray (EECR) is an UHECR with energy exceeding 5×1019 eV (about 8 Joule), the so-called Greisen–Zatsepin–Kuzmin limit (GZK limit).

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Documentary: : Science Bulletins- Aiming High—The Search for Ultra High-Energy Cosmic Rays

From outer space, ultra-high-energy cosmic rays reach Earth. These consist of single sub-atomic particles (protons or atomic nuclei), each with energy levels beyond 1018 eV (about the energy of a tennis ball traveling at 80 km/h[citation needed]). When such a single particle reaches Earth atmosphere, it has its energy dissipated by creating billions of other particles: electrons, photons and muons, all near the speed of light. These particles spread longitudinal (perpendicular to the single particle incoming route), creating a forward moving plane of particles, with higher intensities near the axis. Such an incident is called a "air shower". Passing through the atmosphere, this plane of particles creates UV light, invisible to the human eye, called the fluorescing effect, more or less in the pattern of straight lightning traces. These traces can be photographed at high speed by specialised telescopes, called Fluorescence Detectors, overlooking an area with at a slight elevation. Then, when the particles reach the Earth surface, they can be detected when they arrive in a water tank, where they cause Cherenkov effect: visible blue light. A sensitive photoelectric tube, can catch these impacts. Such a station is called a called water Cherenkov Detector or ‘tank’. The Augen Observatory has both type of detectors covering the same area, which allows for very precise measurements.

 

 

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Malargue, Argentina – prefect height, flat region and population friendly.

water Cherenkov Detector or tank, totally 600 tanks, 3000 km2, 24 telecsope.

The Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra-high-energy cosmic rays: sub-atomic particles traveling at the speed of light and each with energies beyond 1018 eV. In Earth atmosphere, such particle interacts with air nuclei and produces various other particles. These effect particles (called an "air shower") can be detected and measured. But since these high energy particles have an estimated arrival rate of just 1 per km2 per century, the Auger Observatory has created a detection area of 3,000 km2 (1,200 sq mi) — the size of Rhode Island, or Luxembourg — in order to record a large number of these events. It is located in the western Mendoza Province, Argentina, near the Andes.  

17 countries, 300 physicists from nearly 100 institutions around the world, collect and analyse the measured data.

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http://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray

The history of cosmic ray research is a story of scientific adventure. For nearly a century, cosmic ray researchers have climbed mountains, soared in hot air balloons, and traveled to the far corners of the Earth in the quest to understand these energetic particles from space. They have solved some scientific mysteries—and revealed many more. With each passing decade, scientists have discovered higher-energy and increasingly more rare cosmic rays. The Pierre Auger Project is the largest scientific enterprise ever conducted to search for the unknown sources of the highest-energy cosmic rays ever observed.

 

Active galactic cores as one possible source of the particles[edit]

Interactions with blue-shifted cosmic microwave background radiation limit the distance that these particles can travel before losing energy; this is known as the Greisen–Zatsepin–Kuzmin limit or GZK limit.

The source of such high energy particles has been a mystery for many years. Recent results from the Pierre Auger Observatory show that ultra-high-energy cosmic ray arrival directions appear to be correlated with extragalactic supermassive black holes at the center of nearby galaxies called active galactic nuclei (AGN).[3] However, since the angular correlation scale used is fairly large (3.1 degrees) these results do not unambiguously identify the origins of such cosmic ray particles. The AGN could merely be closely associated with the actual sources, for example in galaxies or other astrophysical objects that are clumped with matter on large scales within 100 Mpc.[citation needed]

Some of the supermassive black holes in AGN are known to be rotating, as in the Seyfert galaxy MCG 6-30-15[8] with time-variability in their inner accretion disks.[9] Black hole spin is a potentially effective agent to drive UHECR production,[10] provided ions are suitably launched to circumvent limiting factors deep within the nucleus, notably curvature radiation[11] and inelastic scattering with radiation from the inner disk. Low-luminosity, intermittent Seyfert galaxies may meet the requirements with the formation of a linear accelerator several light years away from the nucleus, yet within their extended ion tori whose UV radiation ensures a supply of ionic contaminants.[12] The corresponding electric fields are small, on the order of 10 V/cm, whereby the observed UHECRs are indicative for the astronomical size of the source. Improved statistics by the Pierre Auger Observatory will be instrumental in identifying the presently tentative association of UHECRs (from the Local Universe) with Seyferts and LINERs.[13]

 

P.S.: further reading :

JEM-EUSO-1wvh76l

Discovering the sources of the particles’ acceleration could offer insight into high-energy astrophysics and the origins of the universe. The project also could reveal clues about “exotic physics,” such as supersymmetry and string theory.

With a grant from the National Aeronautics and Space Administration (NASA), the six teams will accomplish advance work necessary to launch a telescope mounted to the Japanese Experiment Module (JEM) on the International Space Station (ISS).

That launch is scheduled for 2017 and represents the largest collaboration on the ISS, involving the U.S. and 12 other countries. In addition to UWM, the U.S. team, led by the University of Chicago, includes the Colorado School of Mines, Marshall Space Flight Center (MSFC), Vanderbilt University and the University of Alabama-Huntsville.

The goal of the international mission, called the Extreme Universe Space Observatory (JEM-EUSO), is to use the telescope to scan the night skies around Earth from space and record the luminous “tracks” left when these rare particles collide with the Earth’s atmosphere.

http://www5.uwm.edu/news/2013/03/05/uwm-joins-a-nasa-backed-search-for-cosmic-rays-2/#.UlUu2Dj4L1I

http://www.eurekalert.org/pub_releases/2013-03/uoc-nse030813.php

筆記:

1. 能量: 

每秒鐘, 地球每平方米有200條宇宙射線( 能量都比較低, 大概是Most cosmic rays, however, do not have such extreme energies; the energy distribution of cosmic rays peaks at 0.3 gigaelectronvolts (4.8×10−11 J).[9]) 撞擊.  而其間出現有超高能量的宇宙射線卻非常難找到, 它們是出現的次數比較少, 每天發生在每千方公里只有一次(They occur only once per square kilometer of sky per millennium.) , 而能量是Ultra-high energy cosmic rays (UHECRs) are extremely energetic subatomic particles (mostly protons, but also some heavier atomic nuclei) with energies greater than 1015 eV. The record holder so far is a UHECR with an energy of 3×1020 eV – equivalent to a baseball thrown at 160 km/hr!

2.  觀察方法:

因為宇宙射線從外太空進入地球表面, 必經大氣層而發生撞擊後, 產生了 air shower ( 陣雨, the incident particle, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, strikes a molecule in the air so as to produce many energetic hadrons. The unstable hadrons decay in the air speedily into other particles and electromagnetic radiation, which are part of the shower components.)

要觀察宇宙射線和陣雨 air shower, 在地面, The most advanced ground-based experiments to detect cosmic ray showers extend over several kilometres and consist of both Cherenkov detectors monitoring several large tanks of water for light produced by high-energy particles, and fluorescence detectors used to track the glow of the particle as it descends through the atmosphere.

auger-design-graphic

3. 來源:

經過經年的觀察, 我們發現了超高能宇宙射線最有可能是從活動星系核的超大質量旋轉黑洞而來的, 例如 in the Seyfert galaxy MCG 6-30-15[8] with time-variability in their inner accretion disks, 因為旋轉的動態黑洞是最大可能製造這些超高能宇宙射線.

The source of such high energy particles has been a mystery for many years. Recent results from the Pierre Auger Observatory show that ultra-high-energy cosmic ray arrival directions appear to be correlated with extragalactic supermassive black holes at the center of nearby galaxies called active galactic nuclei (AGN).[3] However, since the angular correlation scale used is fairly large (3.1 degrees) these results do not unambiguously identify the origins of such cosmic ray particles. The AGN could merely be closely associated with the actual sources, for example in galaxies or other astrophysical objects that are clumped with matter on large scales within 100 Mpc.[citation needed]

Some of the supermassive black holes in AGN are known to be rotating, as in the Seyfert galaxy MCG 6-30-15[8] with time-variability in their inner accretion disks.[9] Black hole spin is a potentially effective agent to drive UHECR production,[10] provided ions are suitably launched to circumvent limiting factors deep within the nucleus, notably curvature radiation[11] and inelastic scattering with radiation from the inner disk. Low-luminosity, intermittent Seyfert galaxies may meet the requirements with the formation of a linear accelerator several light years away from the nucleus, yet within their extended ion tori whose UV radiation ensures a supply of ionic contaminants.[12] The corresponding electric fields are small, on the order of 10 V/cm, whereby the observed UHECRs are indicative for the astronomical size of the source. Improved statistics by the Pierre Auger Observatory will be instrumental in identifying the presently tentative association of UHECRs (from the Local Universe) with Seyferts and LINERs.[13]

4. 最新消息:

NASA 將會更大的資源去觀察這些超高能宇宙射線

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http://www.eurekalert.org/pub_releases/2013-03/uoc-nse030813.php

Auger combines two techniques for observing cosmic rays. One technique consists mostly of large plastic water tanks, which serve as ground detectors that measure the shape of the shower. Spaced at one-mile intervals, the tanks occasionally intercept a particle from the atmospheric cascade generated by cosmic rays. The particles produce a flash as they cross from air into water. Electronics in the dark tanks detect the light and radios the information to a central station.

The second technique involves four infrared telescopes that detect ultraviolet light emissions generated in the atmosphere by cosmic rays. "You not only see the fluorescence on the ground, but you see the whole shower developing on the atmosphere," Olinto explained.

The Auger telescopes look straight up to the top of the atmosphere, approximately 40 kilometers (24.8 miles) high. "If you go to the International Space Station with the exact same technique and you look down, you can see a lot more of the atmosphere because now you’re 400 kilometers up," Olinto said. "With a 60-degree opening angle, which we are designing, you can see instantaneously a hundred times the Auger area."

Olinto views the Extreme Observatory as the first step toward using the entire Earth atmosphere for studying subatomic particle interactions at energies far exceeding what the most powerful man-made accelerator at the Large Hadron Collider can currently produce. "In my opinion it’s the way to the future," she said.

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