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4 - Quasars and AGN

Published online by Cambridge University Press:  04 May 2023

Kenneth I. Kellermann
Affiliation:
National Radio Astronomy Observatory, Charlottesville, Virginia
Ellen N. Bouton
Affiliation:
National Radio Astronomy Observatory, Charlottesville, Virginia
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Summary

Some celestial objects, later recognized as quasars, were catalogued back in 1887, and their extragalactic nature was discussed as early as 1960. However, the large measured redshift of 3C 48 was rejected, largely because it implied an unrealistically high radio and optical luminosity. Instead it was assumed to be a relatively nearby, less luminous galactic radio star. Following the 1962 observations of lunar occultations of the strong radio source 3C 273 at the Parkes radio telescope and the subsequent identification with an apparent stellar object, Martin Schmidt recognized that 3C 273 had an unmistakable redshift of 0.16. Due to an error in the calculation of the radio position, the occultation position actually played no direct role in the identification of 3C 273, although it was the existence of a claimed accurate occultation position that motivated Schmidt’s 200 inch telescope investigation and his determination of the redshift. Later radio and optical measurements quickly led to the identification of other quasars with increasingly large redshifts, although the nature of the quasar redshifts remained controversial for decades.

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Publisher: Cambridge University Press
Print publication year: 2023

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  • Quasars and AGN
  • Kenneth I. Kellermann, National Radio Astronomy Observatory, Charlottesville, Virginia, Ellen N. Bouton, National Radio Astronomy Observatory, Charlottesville, Virginia
  • Book: Star Noise: Discovering the Radio Universe
  • Online publication: 04 May 2023
  • Chapter DOI: https://doi.org/10.1017/9781009023443.007
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  • Quasars and AGN
  • Kenneth I. Kellermann, National Radio Astronomy Observatory, Charlottesville, Virginia, Ellen N. Bouton, National Radio Astronomy Observatory, Charlottesville, Virginia
  • Book: Star Noise: Discovering the Radio Universe
  • Online publication: 04 May 2023
  • Chapter DOI: https://doi.org/10.1017/9781009023443.007
Available formats
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Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Quasars and AGN
  • Kenneth I. Kellermann, National Radio Astronomy Observatory, Charlottesville, Virginia, Ellen N. Bouton, National Radio Astronomy Observatory, Charlottesville, Virginia
  • Book: Star Noise: Discovering the Radio Universe
  • Online publication: 04 May 2023
  • Chapter DOI: https://doi.org/10.1017/9781009023443.007
Available formats
×