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Introduction
to X-Ray Astrophysics
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The electromagnetic
spectrum and x-rays:
X-rays were first recognized as a new type of radiation by Wilhelm
Conrad Röntgen, a German physicist in 1895. An x-ray is a type
of
electromagnetic radiation with an evergy range of .1 - 100 keV, a
wavelength range of 10 - 0.01 nm and a frequency rane of 30 - 30,000
PHz.
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What makes X-rays?
X-rays can be produced by a number of different processes: they can be
emitted by hot gas, be a product of solar wind interactions , and
emitted when an electron falls an energy level anlong with a a number
of other ways. The UW X-Ray Astrophysics lab focuses mostly on the
three named processes and is working on figuring out their origins.
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Difficulty in studying
x-rays:
Unlike visible light, we can't observe X-rays by just looking at the
sky. The detectors used to research X-rays gather data on the amount of
energy of each X-ray photon, which can be measured with great precision
with a microcalorimeter. This data is then interpreted into a spectrum
and graphed. The spectra can be analyzed to find numerous new data
about the X-rays that had been observed. Unfortunately, the earth's
atmosphere abosorbs these high-energy rays, hindering astronomers'
attempts to learn their secrets. To see X-rays at all, it is necessary
to be above 90% of the earth's atmoshere; and to detect X-rays in the
band where sources are most prominent, all but one millionth of the
atmosphere must be below the instrument. In order to run worthwhile
experiments, rockets are required to lift X-ray detectors above earth's
atmosphere. It is not a trivial matter to build instruments that are
large enough to be sensitive, yet small enough to fit within a rocket.
Instruments have to withstand the rigors of launch but also operate in
a vacuum.
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