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Quasars2 - producing the bizarre spectra he set out to...

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Quasars The two basic things used for studying the far away galaxies are (1) the data encoded in the light received; and (2) our creative minds to interpret what is seen using the laws of physics. Some blue star-like objects appeared to violate those rules. Stars do not produce much energy in the radio band, so when strong radio emission coming from some blue stars was spotted in 1960, astronomers quickly took spectra of the stars in the visible (optical) band to find out the conditions in these strange objects. However, the pattern of lines did not match any of the lines seen in thousands of stellar spectra gathered over a hundred years. Furthermore, the spectra of the blue radio sources did not have absorption lines, but broad emission lines! What a mystery! Which is the quasar and which is an ordinary star? (The quasar is the bright one on the left.) Courtesy of Space Telescope Science Institute Maarten Schmidt solved the mystery in 1963. In order to figure out the structure of the atoms
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Unformatted text preview: producing the bizarre spectra, he set out to construct an energy level diagram from the pattern of the emission lines. He made some mistakes in his calculations because his calculations were not showing the regularity he could clearly see in the spectrum of a radio source called 3C 273 (the 273rd object in the third Cambridge catalog of radio souces). As a test of the regularity he compared the spectrum of 3C 273 with the spectrum of hydrogen. He was shocked because the pattern was the same but greatly redshifted! 3C 273 is moving at a speed of 47,400 kilometers/second (almost 16% the speed of light!). The Hubble Law says that this blue radio object is far outside the Galaxy. The other radio ``stars'' were also at great distances from us. They are called quasi-stellar radio sources or quasars for short. Later, some other blue star-like objects at large redshifts were discovered to have no radio emission, but they are also called quasars ....
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