Detecting Superfast Matter
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- Written by:
- Talya Lerner
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- Scientific consulting by:
- Elizabeth Hays and
- Stefan Funk
- View full credits
Scientists always suspected supernova remnants could speed up cosmic rays, the streams of charged particles that exist throughout space. Now they have proof. NASA’s Fermi Gamma-ray Space Telescope caught two supernova remnants—IC 443 and W44—red-handed as they accelerated cosmic rays to near the speed of light. As cosmic rays travel through the Milky Way galaxy, magnetic fields scramble their paths. By the time the particles reach Earth, the tracks leading back to their source are so complex they’re completely untraceable. So scientists came up with an indirect method for identifying the origins of these particles: observing gamma-ray emissions created by the interaction of accelerated cosmic rays with clouds of interstellar gas. Watch the video to learn more.
For More Information
See NASA.gov
Credits
Please give credit for this item to:
NASA's Goddard Space Flight Center
Cover image courtesy of NASA/DOE/Fermi LAT Collaboration, Tom Bash and John Fox/Adam Block/NOAO/AURA/NSF, JPL-Caltech/UCLA
W44 image courtesy of NASA/DOE/Fermi LAT Collaboration, NRAO/AUI, JPL-Caltech, ROSAT
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Animators
- Scott Wiessinger (KBR Wyle Services, LLC)
- Walt Feimer (KBR Wyle Services, LLC)
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Writers
- Talya Lerner (NASA/GSFC) [Lead]
- Francis Reddy (University of Maryland College Park)
- Scott Wiessinger (KBR Wyle Services, LLC)
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Video editor
- Scott Wiessinger (KBR Wyle Services, LLC)
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Scientists
- Elizabeth Hays (NASA/GSFC) [Lead]
- Stefan Funk (KIPAC) [Lead]
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Producer
- Scott Wiessinger (KBR Wyle Services, LLC)
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Narrator
- Scott Wiessinger (KBR Wyle Services, LLC)
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ID: 11209 Produced Video
Fermi Proves Supernova Remnants Produce Cosmic Rays
Read moreA new study using observations from NASA's Fermi Gamma-ray Space Telescope reveals the first clear-cut evidence that the expanding debris of exploded stars produces some of the fastest-moving matter in the universe. This discovery is a major step toward meeting one of Fermi's primary mission goals.Cosmic rays are subatomic particles that move through space at nearly the speed of light. About 90 percent of them are protons, with the remainder consisting of electrons and atomic nuclei. In their journey across the galaxy, the electrically charged particles become deflected by magnetic fields. This scrambles their paths and makes it impossible to trace their origins directly.Through a variety of mechanisms, these speedy particles can lead to the emission of gamma rays, the most powerful form of light and a signal that travels to us directly from its sources.Two supernova remnants, known as IC 443 and W44, are expanding into cold, dense clouds of interstellar gas. This material emits gamma rays when struck by high-speed particles escaping the remnants.Scientists have been unable to ascertain which particle is responsible for this emission because cosmic-ray protons and electrons give rise to gamma rays with similar energies. Now, after analyzing four years of data, Fermi scientists see a gamma-ray feature from both remnants that, like a fingerprint, proves the culprits are protons.When cosmic-ray protons smash into normal protons, they produce a short-lived particle called a neutral pion. The pion quickly decays into a pair of gamma rays. This emission falls within a specific band of energies associated with the rest mass of the neutral pion, and it declines steeply toward lower energies. Detecting this low-end cutoff is clear proof that the gamma rays arise from decaying pions formed by protons accelerated within the supernova remnants.In 1949, the Fermi telescope's namesake, physicist Enrico Fermi, suggested that the highest-energy cosmic rays were accelerated in the magnetic fields of interstellar gas clouds. In the decades that followed, astronomers showed that supernova remnants were the galaxy's best candidate sites for this process.?A charged particle trapped in a supernova remnant's magnetic field moves randomly throughout it and occasionally crosses through the explosion's leading shock wave. Each round trip through the shock ramps up the particle's speed by about 1 percent. After many crossings, the particle obtains enough energy to break free and escapes into the galaxy as a newborn cosmic ray. The Fermi discovery builds on a strong hint of neutral pion decay in W44 observed by the Italian Space Agency's AGILE gamma-ray observatory and published in late 2011.Watch this video on YouTube. ||
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