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Introduction to High-Energy Astrophysics
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The night sky has always served as a source of wonder and mystery to
people. However, it has only been in the past few decades that we have
truly begun to 'see' the universe in all its glory. This is because we have
only recently been able to look at the universe over the entire
electromagnetic
spectrum.
Instruments to probe the wide range of the electromagnetic (EM) spectrum
have been available to us only in the 20th century, and the rocket age was
required to get instruments sensitive to the
infrared,
ultraviolet,
X-rays,
and gamma-ray
wavelengths
above the Earth. This "view from space" is critical
since radiation
in these ranges cannot penetrate the Earth's atmosphere.
Nevertheless, outside the range
visible to us
with our eyes, the universe produces a vast array of radiation with
wavelengths either too short or too long for our eyes to see. In fact, many
objects in the heavens can be detected only in one of the other regions of the
EM spectrum. And most all objects can only be fully understood by combining
observations of their behavior and appearance in all the different regions.
Putting these pieces of information together allows scientists to begin a full
understanding of the celestial inhabitants.
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