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Space Radiation
by Jeanette Cain
Thanks to advancements in the telescope and new technologies, scientists have observed and recorded radiations from all objects in space, but not only in the form of light. When scientists capture light, they refer to it as the hearing of a single note from a melody. Light is but one part of a whole in the electromagnetic spectrum. Since scientists have "tuned in" to the invisible waves of energy, e.g., radio waves and X-rays, they have discovered a new picture of the universe.
Radiation has movements like waves of the sea. The distance between the crests of these waves is known as the wavelength. Every radiation will have a different wavelength. The highest of frequencies belong to the shortest wavelengths, and they carry the most energy. Frequency refers to the number of waves per second.
With this knowledge, it is known that the high energy sources of the universe will send out short-wavelength radiation. Electrons and antimatter may give off gamma rays, which destroy one another. Gamma rays have the shortest wavelength, which is less than 0.01 nanometers. This is the equivalent to billionths of a meter. The source of this energetic radiation form may come from super-powerful exploding, but distant, stars.
X-rays are given off by the hot gases in the galaxy clusters, compared to the ultraviolet radiation given off by the hot atmospheres of stars. X-rays are between 1 million and 100 million degrees Centigrade. They are usually found around black holes, or between galaxies. Scientists use X ray detectors similar to Geiger counters, but in the form of a telescope. The upper atmosphere will absorb the X-rays. Ultraviolet radiation is given off by the hottest stars. The ozone layer of Earth's atmosphere protects humans from most of the Sun's ultraviolet radiation. This protection also causes an obstruction for astronomers desiring to have a look at the ultraviolet radiation in the universe.
The cooler regions give off long wavelength radiation. Visible light is given off by stars, but the newly hatched stars, planets, and dust clouds give off infrared energy. When electrons speed through magnetic fields of radio galaxies in the distance, radio waves are produced. The radio waves may be given off by supernova remnants, active galaxies, or even the Big Bang. Earth's atmosphere allows radio waves of less than 100 meters to pass to the surface. The longer waves will be reflected back into space as a result of the upper atmosphere. Heat radiation (infrared) is given off by objects with temperatures up to 1,000 degrees Centigrade. The lower atmosphere will absorb some of the wavelengths, but, occasionally, some may be observed from a mountaintop. Light rays (optical radiation) will have wavelengths between 390 and 700 nm (nanometers).
The best studies of wavelengths have been with the help of orbiting satellites. Since the gases in Earth's atmosphere will absorb most of the wavelengths, satellites are able to intercept them before reaching the atmosphere. The Hubble Space Telescope is capable of zooming in to provide sharper images. The only two electromagnetic radiation waves that are incapable of reaching Earth's surface without being absorbed are light and shorter radio waves. While optical telescopes are situated on mountain tops, radio telescopes are built at sea level.
Sources:
1. Couper, Heather and Nigel Henbest. Space Encyclopedia DK Publishing, Inc.: NY 1999
2. Editors. Secrets of the Universe. International Master Publishing: US. 1999
Further Studies:
Hubble Heritage Gallery of Images
Descriptions and images of galaxies photographed by the Hubble.
STSc1 Images
Latest STScl Press Releases and images from Hubble.
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