So what exactly are quasars made up of?
It's true. Unlike distant galaxies, quasars appear pointlike in optical telescopes, so just looking at their visible appearance they are indistinguishable from very faint stars. These visible "stars" were apparently correlated with strong radio sources, but it was hard to be sure that the very faint visible "stars" were the same objects as the radio sources. It was only when astronomers realized that the spectra of these objects were highly redshifted that they became convinced they were something very different.I doubt very much that this is true.
Actually I read that phrase from thisI doubt very much that this is true.At first the astronomers thought they were stars, but further observations showed that they were not stars.
The book was printed in 1962.A good reference on the history is here:
The discovery of quasars in 1963, and more generally, active galactic nuclei (AGN), revolutionized extragalactic astronomy. In early February 1963, Maarten Schmidt (b. 1929; Figure 1) ...