Gamma-rays
are the most energetic form of light and are produced by the
hottest regions of the universe. They are also produced by such
violent events as supernova explosions or the destruction of
atoms, and by less dramatic events, such as the decay of
radioactive material in space. Things like supernova explosions
(the way massive stars die), neutron stars and pulsars, and black
holes are all sources of celestial gamma-rays.
A gamma ray is a packet of
electromagnetic energy--a photon. Gamma photons are the most
energetic photons in the electromagnetic spectrum. Gamma rays
(gamma photons) are emitted from the nucleus of some unstable
(radioactive) atoms.
Gamma rays are an
extremely high-energy form of electromagnetic (EM) radiation.
Gamma ray radiation has a much, much shorter wavelength than
visible light, so gamma ray photons have much, much higher
energies than photons of light do. Gamma rays lie at the extreme
high-energy end of the electromagnetic spectrum. X-rays, which
have slightly lower energies than gamma rays, are the neighbors of
gamma rays along the EM spectrum. In fact, the spectral ranges of
hard X-rays and gamma rays overlap. Gamma rays have wavelengths of
about 100 picometers (100 x 10-12 meters) or shorter, or energies
per photon of at least around 10 keV. This type of electromagnetic
wave oscillates with a frequency of 3 exahertz (EHz or 1018 hertz)
or higher.
There is no sharp
distinction between the highest energy X-rays and the lowest
energy gamma rays. The distinction between X-rays and gamma rays
is actually based on the origin of the radiation, not on the
frequency or wavelength of the electromagnetic waves. Gamma rays
are produced by nuclear transitions, while X-rays are the result
of accelerating electrons. Photons with energies between about 10
keV and a few hundred keV can be either hard X-rays or gamma rays.
These waves are generated by radioactive
atoms and in nuclear explosions. Gamma-rays can kill living cells,
a fact which medicine uses to its advantage, using gamma-rays to
kill cancerous cells. Gamma-rays travel to us across vast
distances of the universe, only to be absorbed by the Earth's
atmosphere. Different wavelengths of light penetrate the Earth's
atmosphere to different depths.
NASA Swift observatory
mission Video
Swift is a
multi-wavelength observatory dedicated to the study of gamma-ray
burst science. Its 3 instruments work together to observe GRBs and
afterglows in the gamma-ray, ultraviolet and optical wavebands.
Gamma-ray bursts
A Gamma-ray burst could wipe out
all living species on the planet Earth at any time with no warning
and destroy the ozone layer in the process. There is no protection for the planet from this fate.
Gamma-ray bursts (GRBs) pose one
of the greatest mysteries of modern astronomy. About once a day,
the sky lights up with a spectacular flash, or burst, of
gamma-rays. More often than not, this burst out shines all of the
other sources of cosmic gamma-rays added together. The source of
the burst then disappears altogether. No one can predict when the
next burst will occur or from what direction in the sky it will
come. At present, we don't exactly know what causes these flashes,
and we've only recently determined how far away they are.
Gamma-ray bursts,
which happen at least once a day, are seen to last for fractions
of a second to minutes, popping off like cosmic flashbulbs from
unexpected directions, flickering, and then fading after briefly
dominating the gamma-ray sky.
A sufficiently close gamma ray
burst could do serious damage to the atmosphere, perhaps wiping
out the ozone layer and triggering a mass extinction.
NASA
GLASTcast - Episode 1: What is GLAST?
Scientists calculated that
gamma-ray radiation from a relatively nearby star explosion,
hitting the Earth for only ten seconds, could deplete up to half
of the atmosphere's protective ozone layer. Recovery could take at
least five years. With the ozone layer damaged, ultraviolet
radiation from the Sun could kill much of the life on land and
near the surface of oceans and lakes, disrupting the food chain.
NASA
GLASTcast - Episode 2: What are Gamma Rays?
Gamma-ray bursts can release
more energy in 10 seconds than the Sun will emit in its entire 10
billion-year lifetime! So far, it appears that all of the bursts
we have observed have come from outside the Milky Way Galaxy.
Scientists believe that a gamma-ray burst will occur once every
few million years here in the Milky Way, and in fact may occur
once every several hundred million years within a few thousand
light-years of Earth.
Studied for over 25 years now
with instruments on board a variety of satellites and space
probes, including Soviet Venera spacecraft and the Pioneer Venus
Orbiter, the sources of these enigmatic high-energy flashes remain
a mystery.
The
Incredible Hulk
"Don't
make me angry. You wouldn't like me when I'm angry."
The Hulk (Dr.
Robert Bruce Banner) is a fictional character, a comic book
anti-hero appearing in publications from Marvel Comics. Created by
Stan Lee and Jack Kirby, the Hulk first appeared in The Incredible
Hulk #1 (May 1962).
The Hulk debuted in
The Incredible Hulk #1 (May 1962), by writer Stan Lee, penciller
and co-plotter Jack Kirby, and inker Paul Reinman. In the first
issue, the Hulk was gray rather than green. Writer and Marvel
editor-in-chief Lee had wanted a color that did not suggest any
particular ethnic group. Colorist Stan Goldberg, however, insisted
to Lee that the coloring technology at the time could not present
the color gray clearly or consistently, resulting in different
shades of gray, and even green, in the issue. From issue #2 (July
1962) on, Goldberg colored the Hulk's skin green.
The Incredible Hulk is a
television series based on the Marvel comic book character of the
same name.
The show ran on CBS from 1978 to 1982, and starred Bill
Bixby as Dr. David Banner and Lou Ferrigno as the Hulk.
David Banner is a
physician/scientist who has been traumatized by the loss of his
wife in a fatal car accident and his guilt over his inability to
save her from the burning wreckage. He begins to conduct research
into strange phenomena in which human beings temporarily display
superhuman levels of strength, trying to understand why others
faced with a traumatic experience similar to his own were able to
save themselves or their loved ones while he was not. He concludes
that high levels of gamma radiation from sunspots are the cause.
To prove the theory, he bombards his body with gamma radiation to
see if he can endow himself with temporary superhuman strength.
Unbeknownst to Banner, the equipment had been upgraded, causing
him to administer a far higher dose than he'd intended. He
initially thinks that the experiment has failed, but later that
evening during a rainstorm, he experiences a flat tire and injures
himself while trying to change it. The resulting pain and anger
trigger his first transformation (which begins with Banner's eyes
turning a whitish-green color) into the Hulk.
Data
compiled from The British Antarctic Study, NASA, Environment Canada,
UNEP, EPA and other sources as stated and credited Researched
by Charles Welch-Updated dailyThis Website is a project of the The
Ozone Hole Inc. a 501(c)(3) Nonprofit Organization
