Halton Arp

Born on 21 March 1927 in New York City, Halton Arp was an award-winning astronomer known for a unique galactic atlas and for his doubts about Big Bang theory. Arp earned his bachelor’s degree from Harvard University in 1949 and his PhD from Caltech in 1953. Over the next three decades, he worked as a staff astronomer at Mount Wilson and Palomar observatories in California. His specialty was seeking out unusual galaxies, and in 1966 he assembled a collection of his observations into a book called The Atlas of Peculiar Galaxies. About the same time, Arp also began noticing a number of galaxy–quasar pairings in which a high-redshift quasar appeared to be unusually close to a low-redshift galaxy. He concluded that a celestial object’s redshift is not necessarily indicative of its cosmic distance, a finding that conflicted with Big Bang cosmology. The so-called redshift controversy put him at odds with many of his peers. His claims could not stand up to subsequent observational evidence, such as the gravitational lensing of high-redshift quasars by lower-redshift galaxies. Arp ended up taking early retirement and joining the Max Planck Institute for Astrophysics near Munich, where he died in 2013. (Photo credit: AIP Emilio Segrè Visual Archives, John Irwin Slide Collection)

Date in History: 21 March 1927