12 - Models with unresolved sources

Summary

Due to the low angular resolution of sources in observations early after the discovery of the CMB, there was a possibility that the radiation’s uniformity and diffuse emission were produced by multiple unresolved very distant sources. This possibility was one of many similar dilemmas in other areas of astronomy and physics, and it was fairly quickly resolved. In the late 1960s, Gold and Pacini suggested the idea of unresolved sources was plausible, while Wolfe and Burbidge, working across the orthodoxy-alternatives divide, addressed the unexplained density of the radiation and its spectral shape by pointing to the possibility of unresolved sources potentially being observable at radio frequencies. However, observational tests demonstrated a lack of suitable objects radiating at predicted frequencies. The epistemic motivation for these and related models was to introduce minimal astrophysical assumptions to explain the nature of the CMB. There was also an anticipation of yet unknown astrophysical objects lurking in the background. Finally, although quickly refuted observationally, a clear and comprehensive model of Rowan-Robinson exhibited all the key features of such models while also anticipating key role of Active Galactic Nuclei in future research.