Paul W. Merrill

Paul Willard Merrill (August 15, 1887 – July 19, 1961) was an American astronomer whose specialty was spectroscopy. He received his Ph.D at the University of California in 1913. He spent the bulk of his career at Mount Wilson Observatory, from which he retired in 1952. He studied unusual stars, particularly long-period variable stars, using spectroscopy. He also studied the interstellar medium. Shortly before he retired, he succeeded in detecting technetium in the variable star R Andromedae and other red variables. Since technetium has no stable isotopes, it must have been produced recently in any star in which it is found, and this is direct evidence of the s-process of nucleosynthesis.