ASTRO Summary 5
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University of Illinois, Urbana Champaign *
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Astronomy
Date
Jan 9, 2024
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docx
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Uploaded by EarlThunderDugong10
“Extreme Astrophysics: The Gamma Ray Universe” by Lynn Cominsky
This article delves into the mysterious world of gamma rays and the way they interact with the
world around us. After describing the nature of gamma rays and how they are studied, the article
analyzes their source and the startling ways studying gamma rays has changed our view of the universe.
Finally, the article describes the potential for using gamma rays to better understand many of the
mysteries still puzzling scientists, including the presence of dark matter.
The first most important takeaway from this article is the method through which gamma rays are
captured and studied. While there exist many methods of studying gamma rays, such as directing
incoming gamma rays into crystals such that when the crystals emit light the gamma ray’s origin could be
found, the most accurate method is called pair conversion. In this process, a dense material is set up
such that when a gamma ray hits it, the ray is split into an electron and positron whose movements can
be used to reconstruct the incoming direction of the gamma ray thereby discovering its origin. All of this
information can only be found via computers able to sort through all the other noise and signals to find
the few real gamma rays. What scientists have found through this research is that most viewed gamma
rays are non-thermal in the sense they are not seen from something that is glowing, a big difference
from most of the light wavelengths that we can observe. Instead, gamma rays come from the
acceleration of cosmic rays which produce gamma rays when they crash into gas and concentrated dust.
This brings us to the next big takeaway which are the significant discoveries of NASA’s Fermi mission in
our current understanding of the gamma-ray universe. Equipped with multiple methods of detecting
gamma rays, Fermi has helped scientists discover that gamma-ray bursts, which are tremendously
energetic explosions in space that emit tons of gamma radiation, longer than 2 seconds come from
massive dying stars and that those shorter than 2 seconds come from neutron stars crashing together.
Fermi has also detected such gamma ray bursts to support this conclusion. These discoveries are
extremely important, as they have helped explain how almost half of the universe’s supply of heavy
elements form. Fermi also helped discover Fermi Bubbles, which are nearly symmetric diffuse gamma
ray lobes stretching from above and below the Milky Way’s center, suggesting that in the past, there
were explosive outburst of energy from the center of the Milky Way. The final takeaway from this article
is the exciting future of gamma-ray astronomy and its potential in explaining the existence and nature of
dark matter. Although Fermi has detected an uptick in gamma rays originating from the center of the
Milky Way and Andromeda Galaxies, scientists have been unable to determine whether they are from
dark matter or from undetected stars. The hope is that through newer generations of satellites, we will
be able to gain a better understanding of the nature of gamma rays and their relation to dark matter.
Additionally, over a quarter of gamma radiation emitting objects detected by Fermi are classified as
unknown. Once again, scientists hope that more precise instruments will eventually be able to
determine what these objects are.
Overall, I found this article to be a tough read and had to go back multiple times to understand
the concepts being discussed. However, it was extremely interesting and I loved the discussion of dark
matter at the end and its potential gamma ray emitting capabilities. I also really appreciated the pictures
and diagrams included in the article, they were extremely helpful and helped clarify many questions I
had about gamma rays. However, I do have a few remaining questions about gamma rays:
Since gamma
rays are the most energetic form of electromagnetic radiation, can their energy be practically harnessed
for power generation? Could gamma rays be used to create a better dating system of the age of the
universe, stars, and other planetary material? How hazardous are gamma rays? If there was a directed
burst of gamma radiation towards Earth, would we be safe?
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