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3500 4000 4500 5000 5500 6000 6500 7000 Wavelength, Angstroms

3500 4000 4500 5000 5500 6000 6500 7000 Wavelength, Angstroms source in the 3rd Cambridge catalog of radio sources.) When photographs of the area around the radio source were examined, a faint (13th magnitude) star was noted. This was an interesting discovery, since no radio stars were known at the time. Closer observations, producing photographs like that in Fig. 19.17, have shown that 3C273 is not really a star. It looks like a star with a fuzzy patch around it. The most detailed photographs show a jet extending from the core, just as in radio galaxies.

The optical spectrum of 3C273, shown in Fig. 19.18, is quite unusual. The spectrum puzzled astronomers for some time. It was finally noted that a series of lines looked like the Balmer series, but with a very large redshift. For example, the

Fig 19.16.

Markarian 421, showing its full spectrum over all wavelength ranges. [William Keel, University of Alabama]

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