Each type of electromagnetic radiation is produced by certain - TopicsExpress



          

Each type of electromagnetic radiation is produced by certain conditions. Astronomers can now detect all these types of emissions, sometimes by telescopes on the ground. Some forms such as X-rays can only be detected by telescopes in space as our atmosphere absorbs them, preventing them from reaching the Earths surface. By detecting and studying electromagnetic emissions, astronomers can determine the conditions that produced them and so increase our understanding of objects and conditions far out in space. There are two basic forms of radio emission thermal and non-thermal: -Thermal emissions are caused by the motion of charged objects such as molecules and atoms. As all matter has some heat energy stored in it, atoms vibrate, emitting electromagnetic radiation. The more energy stored, the more the atoms vibrate and the greater the amount of radiation emitted.nother form of thermal emission is due to the spin of electrons as they orbit a nucleus. An excited electron loses energy by flipping it spin back to a more stable state. The radio wave emitted in this process always has a specific discrete wavelength. An electron in a neutral hydrogen atom, for example, produces radio waves of 21cm wavelength via this process. As hydrogen is the most abundant element in the Universe this 21cm hydrogen line was one of the first radio emissions detected from space and continues to be a key wavelength for astronomers to observe. -Non-thermal sources of radio waves include synchrotron radiation, in which electrons moving near the speed of light get accelerated in strong magnetic fields. Such conditions occur in very powerful sources such as quasars, active galactic nuclei and supernova remnants, the remains of massive stars that have exploded. Geosynchrotron emissions are a related process produced by pulsars, rapidly spinning neutron stars that are remnants of more massive stars. Masers or microwave amplification by the stimulated emission of radiation are similar to lasers but at short wavelength radio frequencies or microwaves instead of visible light. Natural maser sources are sometimes found in clouds of molecules in regions where stars are forming.
Posted on: Fri, 18 Oct 2013 21:21:39 +0000

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