The galaxy NGC 4319 and the quasar Markarian 205 were linked in the mind of famed astronomer Halton Arp.
The galaxy NGC 4319 and the quasar Markarian 205 (top right) were at the center of a years-long debate over the validity of redshifts. Credit: STScI
The astronomer Halton C. Arp (1927–2013) was a very well-known researcher of galaxies and other distant objects. He is celebrated for a number of reasons, not the least of which is his magnificent Atlas of Peculiar Galaxies, published in 1966. I was privileged to know “Chip” Arp, as he was known, and he was a superbly nice fellow.
But Arp was also in the center of a longstanding controversy that essentially derailed his career. In the 1970s he wrote a great deal about redshifts, the measurement by which one can determine the distances of objects like galaxies. He became fixated on a galaxy/quasar pair, NGC 4319 and Markarian 205, in Draco. “Here we have a galaxy/pair connected by a light bridge that overturns the reliability of redshift as a distance indicator,” he famously wrote.
The measured distances to NGC 4319 (galaxy) and Markarian 205 (quasar) are 77 million light-years and 1 billion light-years, respectively. They lie extremely close to each other on the sky, and Arp was convinced that a “light bridge” connected them, meaning they could not be at such different distances.
After many years of papers, publishing, and arguments, it became clear that the distances are correct and the so-called light bridge was an artifact of the imperfect resolution in images at the time. In the end, the quasar was shown to be 14 times more distant, and sadly, Arp left the United States and finished his career in Europe, essentially having been left out of observing time from U.S. telescopes.
