- 2937 - COSMIC RAYS - where do they come from? Cosmic rays are mostly protons, the nucleus of atoms that have a positive electrical charge. They are traveling at near light speed and are entering Earth’s atmosphere and your very own body every second.
------------------ 2937 - COSMIC RAYS - where do they come from?
- These mysterious cosmic rays are traveling at speeds approaching the speed of light and are constantly pelting Earth’s upper atmosphere from the depths of space. These high speed particles are creating high-energy collisions that dwarf those produced in even the most powerful particle colliders. These atmospheric particle crashes rain down gigantic showers of secondary particles to the surface of Earth.
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- Despite being discovered more than a century ago, physicists still don’t know where these cosmic rays come from. The short answer as to why we can’t trace cosmic rays back to their source is magnetic fields.
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- These charged cosmic-ray particles are redirected by the magnetic fields as they pass through their long journey through space. As magnetic fields in space have local, small, randomly oriented structures, a prediction of the exact path of a cosmic-ray particle is impossible.
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- Cosmic rays are comprised of extremely energetic charged particles that may include protons, alpha particles, and atomic nuclei like helium and iron, with miniscule proportions of antiparticles. Alpha particles are two protons and two neutrons bound together, that is the nucleus of helium.
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- The first discovery of cosmic rays was in the early 1900s. The energies of these particles were monumental in comparison to those of every other particle observed until that point.
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- The average energy of a solar photon is approximately 1.4 electron volts (eV). For reference, a flying mosquito has an energy of about 1 trillion eV, or 10^12 eV, but a mosquito is also much, much larger than a single particle.
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- Meanwhile, an alpha particle emitted during the decay of Uranium-238 possess 4.27x10^6 eV of energy. Compare that to a cosmic ray proton, which has an energy of some 10^20 eV.
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- Imagine a proton that is accelerated so that it has an energy of 100 Joule. This energy corresponds to that of a tennis ball smashed by someone with a velocity of around 124 miles per hour. Only, the tennis ball is 10^29 times heavier than the proton.
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- That means a proton can only reach that extreme, macroscopic energy by traveling at almost the speed of light. The universe must be able to accelerate particles to these energies, but we still do not know how it does it. The processes that accelerate cosmic rays to such astounding energies must result from powerful and violent events, which considerably narrows down possible sources.
- One of the best ways of accelerating particles is a shock front that occurs when a medium with a large velocity runs into a slower one, producing a shock wave, a sudden change in the properties of the medium.
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- In the case of the universe, the changed properties are velocity and density, and even magnetic fields. Luckily for the cosmic rays, the field becomes highly turbulent in that process. And the combination of a shock front with turbulence is a great particle accelerator.
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- One likely suspect that could produce such a shock front is “supernovae“. As a shell of shocked material blasted away from an exploding star, it hits the cool interstellar medium that lies between stars, almost like a cosmic tsunami.
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- Traveling shock fronts can also be found in active galaxies, where huge plasma jets exist. Supernova remnants and active galaxies are the most promising candidates for cosmic-ray acceleration.
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- For this reason, better understanding cosmic rays, as well as their origins, is expected to open an important window into tremendously powerful and awe-inspiring cosmic events, such as supernovae and collisions between blackholes and neutron stars.
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- It was August 1912 when Austrian-American physicist Victor Hess began a series of flights to the upper atmosphere in a hydrogen-filled balloon equipped with an electroscope. His aim was to take measurements of ionizing radiation.
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- At the time, it was widely believed that radiation from the Earth itself was responsible for this phenomenon of knocking electrons off atoms. Should this be the case, however ionization should be strongest near the planet’s surface. That’s not what Hess found.
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- Hess discovered something startling. At a nosebleed-inducing altitude of 3.3 miles ionization rates of the air were three times that measured at sea level. He concluded that the source of this ionization was not coming from below our feet, but instead from above.
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- Further measurements made during a solar eclipse also showed the Sun wasn’t the source of this ionization radiation. During the course of seven balloon trips, Hess discovered cosmic rays, confirmed and named by Robert Millikan in 1925, coming from beyond our solar system.
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- The detection of cosmic rays has been associated with balloon flights ever since, the upper atmosphere isn’t the most convenient laboratory to investigate the high-energy particle collisions they produce. To study the collisions caused by cosmic rays, particle physicists retreated below ground, employing increasingly monstrous particle accelerators to slam together particles in an attempt to replicate the collisions that cosmic rays spark in the upper atmosphere.
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- This quest has culminated with CERN’s “Large Hadron Collider” (LHC) with a 16-mile circumference deep beneath the French/Swiss border. Yet, despite its impressive size, power and utility, the LHC still can’t reach the energies produced by cosmic ray collisions.
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- At roughly the same time a thrilling balloon ride changed our perspective of the universe forever, a physicist named Einstein was working on a wild theory that would radically change our understanding of the fabric of space-time.
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- The discovery of gravitational waves , ripples in space-time predicted by Einstein’s theory of general relativity, has made a new form of astronomy possible, allowing us to investigate events and objects that we could never hope to observe in the electromagnetic spectrum alone.
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- This combination of electromagnetic or “traditional” astronomy and gravitational-wave detections, along with detecting neutrinos, which are ghost-like particles with virtually no mass or electric charge, is known as multi-messenger astronomy. It has a significant role to play in future investigations of cosmic rays, and, by extension, the high-energy universe.
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- The gravitational-wave signal came from the merger of two neutron stars and was observed in 2017. It was significant for both multi-messenger astronomy and identifying potential sources of cosmic rays. Not only did this violent merger become the first such event to be detected in both gravitational waves and electromagnetic radiation, but it also confirmed that the merger of compact stellar remnants can accelerate particles to great speeds, creating cosmic rays.
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- Work on the connection of neutrino emission and gravitational waves promises a long-term gain in the understanding of not only the merger of neutron stars, but also supermassive binary black holes that can represent the core of many active galaxies.
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- There is no other way than multi-messenger astronomy to understand the origin and impact of cosmic rays. Cosmic rays alone cannot give an answer, neither can gamma-rays or neutrinos for themselves. All three messengers have unique properties and show different parts of a big puzzle. Only by putting together all the pieces, can we see the full picture.
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- In the meantime astronauts in space need protection from these destructive cosmic rays. A team of MIT researchers sent samples of various high-tech fabrics, some with embedded sensors or electronics, to the International Space Station. The samples will be exposed to the space environment for a year in order to determine a baseline for how well these materials survive the harsh environment of low Earth orbit.
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- The hope is that this work could lead to thermal blankets for spacecraft, that could act as sensitive detectors for impacting micrometeoroids and space debris. Ultimately, another goal is new smart fabrics that allow astronauts to feel touch right through their pressurized suits.
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- The white color of the International Space Station is actually a protective fabric material called ‘Beta cloth“, which is a Teflon-impregnated fiberglass designed to shield spacecraft and spacesuits from the harsh elements of low Earth orbit. For decades, these fabrics have remained electrically passive, despite offering large-area real estate on the exterior of space assets.
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- We imagine turning this spacecraft skin into an enormous space debris and micrometeoroid impact sensor. Materials like charge-sensitive synthetic fur and vibration-sensitive fiber sensors our project’s focus into space-resilient fabrics. The resulting fabric may be useful for detecting cosmic dust of scientific interest, and for damage detection on spacecraft.
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- In one year, these samples will return to Earth for post flight analysis. We’ll be able to measure any erosion from atomic oxygen, discoloration from UV radiation, and any changes to fiber sensor performance after one year of thermal cycling.
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- There is some chance that we will also find hints of micron-scale micrometeoroids. We’re also already preparing for an electrically powered deployment currently scheduled for late 2021. At that point we’ll apply an additional protective coating to the fibers and actually operate them in space.
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- The fabric contain thermally drawn “acoustic” fibers developed that are capable of converting mechanical vibration energy into electric energy, via the piezoelectric effect.
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- When micrometeoroids or space debris hit the fabric, the fabric vibrates, and the “acoustic” fiber generates an electrical signal. Thermally drawn multimaterial fibers have been developed by our research group at MIT for more than 20 years; what makes these acoustic fibers special is their exquisite sensitivity to mechanical vibrations.
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- The fabric has been shown in ground facilities to detect and measure impact regardless of where the space dust impacted the surface of the fabric. In 2019, an isotopic signature for this type of interstellar dust was discovered in fresh Antarctic snow, so we believe that some of this dust is still whizzing around the solar system, holding clues about the dynamics of supernova explosions.
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- The hope is to see advanced fibers and fabrics tackle other questions of fundamental physical interest in space, maybe by leveraging optical fibers or radiation sensitive materials to create large aperture sensors.
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- They have developed a conceptual prototype in which sensory data on the exterior skin of a pressurized spacesuit armband is mapped to haptic actuators on the wearer’s biological skin. Using this system, astronauts will be able to feel texture and touch right through their spacesuits! This direct experience of a new environment is very central to humanity’s drive to explore.
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- An impact-sensitive skin can also be used for damage detection on space craft. The fabric’s ability to localize damage from space debris and micrometeoroids is how we will really sell the concept to aerospace engineers.
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- Although the space age began 63 years ago when Soviet Union’s Sputnik 1 was launched into an elliptical low Earth orbit, many unanswered questions remain regarding the effect of the space environment on humans, as well as the safety of astronauts as they operate in the space environment.
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- Future spacesuits will be electrically active and highly multifunctional. Textiles buried within the suit will be able monitor the health condition of astronauts in real time by interrogating physiological signals over large areas.
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- Fabrics may also serve as localized heating and cooling systems, radiation dosimeters, and efficient communications infrastructure via fabric optics and acoustics.
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- Fabrics may harvest solar energy as well as small amounts of energy from vibration, and store this energy in fiber batteries or supercapacitors, which would allow the system to be self-powered. Fabrics might even serve as part of an exoskeleton that assists astronauts in maneuvering on planetary bodies and in microgravity.
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- Space is a new frontier for research, while lots of terrestrial applications have been envisioned in ambient conditions and even under water. From low Earth orbit to planetary bodies, space is a unique environment with atomic oxygen, radiation, high speed impactors, and extreme temperature cycling.
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---------------------See Review 2858 for a list of many more reviews about cosmic rsays:
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- December 13, 2020 COSMIC RAYS 2937
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--------------------- --- Wednesday, December 16, 2020 ---------------------------
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