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Gamma rays (often denoted by the Greek
letter gamma) are an energetic form of
electromagnetic radiation produced by nuclear or subatomic
processes such as
electron-position
annihilation or cobalt-60 decay. They have
electromagnetic
frequencies in the range of 30 Petahertz (1015
hertz) to 60 Exahertz (1018
hertz) and are more penetrating than either
alpha
or beta
radiation,
but less
ionizing. Gamma rays are
distinguished from
X-rays by
their origin. Gamma rays are produced by nuclear transitions while
X-rays are
produced by energy transitions due to accelerating
electrons. Because it is possible for some
electron transitions to be of higher energy than nuclear
transitions, there is an overlap between low energy gamma rays and
high energy
X-rays.
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ionization, gamma radiation interacts with matter via
three main processes: the photoelectric effect, Compton
scattering and pair production. Gamma rays, like
X-rays,
are mutagenic and destructive to organic tissue. Prolonged or
intense exposure can cause burns and cancer. The atmosphere of
Class M planets, however, readily absorb large amounts of
X-rays
and gamma rays, making them largely opaque to these damagingly
high
frequency
electromagnetic waves.
Gamma rays are sometimes divided
into subsets to designate different
frequency ranges between 30 Petahertz and 60 Exahertz. One
of these
frequency bands is called "E-band"
radiation, and is commonly emitted by collapsing stars. |
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