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Halton C. Arp (1927–2013)

Published onDec 01, 2013
Halton C. Arp (1927–2013)

AIP Emilio Segrè Visual Archives,
John Irwin Slide Collection

Independent thinking and unorthodox opinions developed early in Halton (Chip) Arp’s life. He was born on March 21st, 1927, to parents living in Greenwich Village, New York. His father was an artist and moved around during Chip’s early years, so he did not go to school until he was ready for the fifth grade. He was stimulated by his father’s artistic friends and was clearly an intelligent, perhaps even precocious, child. He read widely and at a high level --he recalled having read works by Bertrand Russell and Sigmund Freud, but he had not learned the multiplication tables! Once these had been mastered he was quickly promoted to the seventh grade. As he himself said, he found it difficult to socialize with the other students after having studied for so long on his own. Nevertheless, he went on to two years in a public high school, and then left home at the age of 16 to board in Tabor Academy. World War II was not yet over when he finished there, so he served in the U.S. Navy for about a year, where he received an intensive training in practical electronics. He then went to Harvard University determined to study astronomy and immediately came under the influence of Bart Bok. Arp graduated from Harvard at about the end of Shapley’s long reign there, and Bok advised him to go to Cal. Tech. for his graduate work. When Chip demurred, wishing to stay at Harvard, Bok, clearly with psychological insight, said that perhaps the academic standard at Cal. Tech. was too high for him. To Cal. Tech. Chip went!

He began to show his independence at Cal. Tech. proposing a thesis topic of his own choosing, which was promptly shot down by both Baade and Minkowski. He also bridled at being labelled an astrophysicist, much preferring to be called an astronomer (a preference which I share). Nevertheless, he duly received his Ph.D. in 1953. Chip then spent two years at Mount Wilson searching for novae in the Andromeda Galaxy. He did not think that this was a very important programme, but Hubble and Baade both wanted it done and, correctly or not, Chip sensed that they thought he was somewhat unstable and that in order to have the chance to do independent research later he had to take on a routine job of some sort. At the end of that time, they proposed to him a teaching post at a local college, but Chip was set on doing research and, by arrangement with Frank Edmondson, he went to Indiana on an NSF grant which was actually tenable in South Africa. There he worked for two years (1955-57) at the Radcliffe Observatory in Pretoria and the Royal Observatory at the Cape of Good Hope. His research there led him to his first controversial conclusion, that the stars in the Magellanic Clouds were metal-poor compared with those in our own Galaxy. My first chance meeting with Chip was en route to the IAU General Assembly in Moscow in 1958, when we sat next to each other on an Aeroflot plane from Helsinki to what was then Leningrad. A few days later, I heard him present the results of his Magellanic-Cloud research, to be followed immediately by Michael Feast who concluded that there was no difference in the chemical compositions of stars in the Clouds and in our Galaxy!

By the time of that meeting in Moscow, however, Chip had returned to Mount Wilson and Palomar Observatories as an Assistant Astronomer. At first, his work was mostly on globular clusters, novae, stellar populations and stellar evolution, but he had always wanted to work on galaxies and eventually he was able to break into that field. To understand his approach to the study of galaxies, it is necessary to recall that he began at a time when the astronomical community was by no means unanimous in believing Big-Bang cosmology to be essentially correct. Until the discovery of the cosmic background radiation in 1965, the community was about equally divided between those who accepted the Big-Bang theory and those who accepted a steady-state theory. Moreover, in the early 1960s little was known about galaxy formation. Chip’s Atlas of Peculiar Galaxies, probably the one of his publications that has had the most impact on his colleagues, was undertaken because he believed that the peculiar galaxies would throw light on the way in which galaxies were formed. Although this was published in 1966, after the discovery of the cosmic background radiation, clearly it was conceived and in large part completed before that discovery became known. Chip became convinced that these peculiar galaxies were ejecting material that would eventually grow into new galaxies –an idea that had been anticipated by Ambartsumian almost a decade earlier. Ironically, today’s users of the Atlas see the galaxies depicted there as examples of the merging of galaxies!

After the discovery of quasars and their high red-shifts, Chip was by no means the only person to question whether those red-shifts were true Doppler shifts and cosmological in origin. He continued to dissent, however, long after most workers in the field had become convinced that quasars are indeed very distant objects. Chip believed that he had found evidence that quasars had been ejected from galaxies and that the observed red-shifts contained an intrinsic component and were not reliable indicators of distance. As the majority of cosmologists solidified in their belief in Big-Bang cosmology and in the cosmological interpretation of quasar red-shifts, Chip found himself increasingly at odds with his former friends and colleagues. This eventually led to his leaving the Mount Wilson and Palomar Observatories and accepting an appointment at the Max Planck Institute for Astronomy and Astrophysics in Munich, Germany, where he resided until his death on December 28th, 2013. In 1960, he received the Helen Warner Prize of the American Astronomical Society and the Newcomb Cleveland Prize for an address on “The Stellar Content of Galaxies” given to a joint session of the Society and the American Association for the Advancement of Science, Section D. In 1984, he also received an Alexander von Humboldt Senior Scientist Award.

During one of the few long conversations that I had with Chip he told me that he could perfectly well understand why people disagreed with his conclusions about red-shifts, but he could not understand the anger that he sensed in referee’s reports. Of course, I have not seen the reports and do not know who wrote them. If some referees were angry, it may be because they felt that Chip was stubborn. Perhaps there was a stubbornness in his make-up, but there was also a deep conviction that the observational science of astronomy is different in kind from the experimental science of physics. He came to feel, rightly or wrongly, that the mainstream cosmologists were confusing the two kinds of science and that the focus on red-shifts as being always distance indicators led them to ignore alignments and associations that he saw on the sky. His critics, of course, either denied that the alignments existed or asserted that they were not statistically significant. There is no doubt that the overwhelming majority of astronomers now believe that Chip was wrong and the consensus is that Big-Bang cosmology is all but proven; but the issue is greater than whether he was right or wrong. Consensus represents the best knowledge we have in scientific matters and it is unwise to ignore it; but it can be, and sometimes has been, wrong. A century ago, the consensus among astronomers was that hydrogen could not be a major constituent of the Sun and stars and Celia Payne, as she was then, had great difficulty in convincing the leading astronomers of the day otherwise. We do not know what ideas that seem wrong to us today will be accepted wisdom a century from now. Chip’s real legacy is to remind us that we should keep our minds open to the possibility that even our most cherished theories may be mistaken.

Author note: In writing this obituary, I have made considerable use of the transcript of an interview of Halton Arp by Paul Wright on 1975 July 29, Niels Bohr Library and Archives, American Institute of Physics, College Park, MD, USA. The transcript may be found on the following web-site:

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