Dec. 31, 1864: The birth of Robert Aitken

Today in the history of astronomy, the great discoverer of binary stars is born.
By | Published: December 31, 2025

Robert Aitken's name may also be familiar from references to the Moon's South Pole-Aitken Basin -- the basin that stretches from the Moon's south pole to Aitken Crater (named for Robert Aitken). Credit: NASA/GSFC/Arizona State University
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Key Takeaways:

  • Robert Aitken, born in 1864, overcame childhood health challenges, including progressive deafness, to earn a B.A. in mathematics in 1887 and subsequently teach mathematics and astronomy.
  • He embarked on a distinguished 40-year tenure at Lick Observatory, progressing from assistant astronomer to associate director, and eventually becoming the observatory's director in 1930.
  • Aitken achieved prominence for his extensive research on double stars, discovering over 3,100 new binaries and compiling the authoritative *New General Catalogue of Double Stars Within 120° of the North Pole*, widely recognized as the Aitken Double Stars (ADS) catalog.
  • His lasting impact is reflected in the continued use of ADS numbers for identifying binary stars, and he was further honored with the Bruce Medal, the Gold Medal of the American Astronomical Society, and served as president of the Astronomical Society of the Pacific.
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Born Dec. 31, 1864, in California, Robert Aitken was frequently ill as a child, with severe ear infections that eventually led to progressive deafness. Despite his education being delayed by his health until he was nine and his plans to become a preacher, Aitken graduated with a B.A. in mathematics in 1887. He taught math and astronomy at Livermore College and the University of the Pacific for some time, before moving to Mount Hamilton to study at Lick Observatory. There he was offered a one-year appointment – and ended up staying for 40 years, as assistant astronomer, associate director, and beginning in 1930, the director of the observatory.

Aitken became famous for his double star research, discovering over 3,100 new binaries. He authored the New General Catalogue of Double Stars Within 120° of the North Pole, a reference commonly known as the Aitken Double Stars (ADS) catalog. ADS numbers are still used to identify some binaries. He also served as the president of the Astronomical Society of the Pacific, and earned the Bruce Medal and the Gold Medal of the American Astronomical Society.

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