- 3272 - COSMIC RAYS - messengers from space? New findings in August 2021 suggest that carbon, oxygen, and hydrogen cosmic rays travel through the galaxy toward Earth in a similar way, but, surprisingly, that iron arrives at Earth differently. Learning more about how cosmic rays move through the galaxy helps address a fundamental, question: How is matter generated and distributed across the universe?
--------------------- 3272 - COSMIC RAYS - messengers from space?
- Cosmic rays are atomic nuclei stripped of their electrons are constantly traveling through space at nearly the speed of light. They enter Earth's atmosphere at extremely high energies. Information about these cosmic rays can give scientists clues about where they came from in the galaxy and what kind of event generated them.
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- An instrument on the International Space Station (ISS) called the Calorimetric Electron Telescope (CALET) has been collecting data about cosmic rays since 2015. The data include details such as how many and what kinds of atoms are arriving, and how much energy they're arriving with.
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- Cosmic rays arrive at Earth from elsewhere in the galaxy at a huge range of energies, from 1 billion volts to 100 billion - billion volts. The CALET instrument is one of extremely few in space that is able to deliver fine detail about the cosmic rays it detects.
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- A cosmic ray spectrum shows how many cosmic rays are arriving at the detector at each energy level. The spectra for carbon, oxygen, and hydrogen cosmic rays are very similar, but the key finding is that the spectrum for iron is significantly different.
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- There are several possibilities to explain the differences between iron and the three lighter elements. The cosmic rays could accelerate and travel through the galaxy differently.
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- The way the elements get from the sources to us is different, but it may be that the sources are different as well. Scientists generally believe that cosmic rays originate from exploding stars (supernovae), but neutron stars or very massive stars could be other potential sources.
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- By the time cosmic rays reach our instruments, they have already interacted with Earth's atmosphere and broken down into secondary particles. With Earth-based instruments, it is nearly impossible to identify precisely how many primary cosmic rays and which elements are arriving, plus their energies. But CALET, on the International Space Station above the atmosphere, can measure the particles directly and distinguish individual elements precisely.
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- Elements on their way to Earth, cosmic rays, can break down into secondary particles, and it can be hard to distinguish between original particles ejected from a source (like a supernova) and secondary particles. That complicates deductions about where the particles originally came from.
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- As things interact on their way to us, then you'll get essentially conversions from one element to another. Iron is unique, in that being one of the heaviest things that can be synthesized in regular stellar evolution. Iron is the only pure primary cosmic ray, where with others you'll have some secondary components.
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- Measuring cosmic rays gives scientists a unique view into high-energy processes. The cosmic rays arriving at CALET represent the stuff we're made of. We are made of stardust. And energetic sources, things like supernovas, eject that material from their interiors, out into the galaxy, where it's distributed, forms new planets, solar systems, and, you and me.
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- The study of cosmic rays is the study of how the universe generates and distributes matter, and how that affects the evolution of the galaxy. Studying cosmic rays is studying the astrophysics of this engine we call the Milky Way that's throwing all these elements around.
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- The Japanese space agency launched CALET and today leads the mission in collaboration with the U.S. and Italian teams.
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- CALET was optimized to detect cosmic ray electrons, because their spectrum can contain information about their sources. That's especially true for sources that are relatively close to Earth in galactic terms: within less than one-thirtieth the distance across the Milky Way.
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- CALET also detects the atomic nuclei of cosmic rays very precisely. Now those nuclei are offering important insights about the sources of cosmic rays and how they got to Earth. The latest finding creates more questions than it answers, emphasizing that there is still more to learn about how matter is generated and how it moves around the galaxy.
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- How do you make matter? How does the universe work? The more we learn the more questions there are.
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- September 12, 2021 COSMIC RAYS - messengers from space? 3272
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