Horace Welcome Babcock

Horace Welcome Babcock


Date of Birth
September 13, 1912
Date of Death
August 29, 2003

Horace Babcock was born in California and earned his B.S. at the California Institute of Technology and his Ph.D. at the University of California at Berkeley. For his doctorate he determined the rotation curve of the Andromeda Galaxy M31, showing that the mass to light ratio increased going outward from the nucleus. Much later his measurements would be considered an early indication of the existence of dark matter. After a stint at the Yerkes and MacDonald Observatories, where he designed a fast nebular spectrograph, and war work at MIT and Caltech, Babcock joined the staff of the Mt. Wilson (soon to be Mt. Wilson and Palomar) Observatory in 1946. There he invented and built many astronomical instruments, including the solar magnetograph, and microphotometers, automatic guiders, and exposure meters for the 100 and 200-inch telescopes. He often worked closely with his father, Harold Babcock, whom he succeeded in 1948 as head of the diffraction grating laboratory, the builder of the world’s best gratings at the time. The two Babcocks were first to measure the distribution of magnetic fields over the solar surface. By combining his polarizing analyzer with the spectrograph Horace Babcock discovered magnetic fields in other stars. He developed important models of sunspots and their magnetism, and in 1953 he was the first to propose adaptive optics. He directed the Mt. Wilson and Palomar (later Hale) Observatories from 1964 to 1978. During this time he led in founding the Las Campanas Observatory in Chile. He continued working on innovative projects in instrumentation after retirement.

Presentation of Bruce medal

Abell, George W., PASP 81, 179-83 (1969).

Other awards

American Astronomical Society Solar Physics Division, George Ellery Hale Prize, 1992.
National Academy of Sciences, Henry Draper Medal, 1957.
Royal Astronomical Society, Eddington medal, 1958; Gold medal 1970, presented by B. Lovell, QJRAS 11, 85-87 (1970). See also Physics Today 23, 5, 91 (1970).

Biographical materials

A Dictionary of Scientists (Oxford University Press, Oxford, UK, 1999).
Observatories of the Carnegie Institution of Washington, Horace Babcock Memorial Symposium
Preston, George W., Biographical Memoirs of the National Academy of Sciences (2008).


Baliunas, Sallie, Mercury 32, 6, 45 (Nov/Dec 2003).
McFarling, Usha Lee, Los Angeles Times, 3 September 2003.
O’Connor, Anahad, New York Times, 5 September 2003
Preston, George W., PASP 116, 290-94 (2004).
Sandage, AllanProceedings of the American Philosophical Society 150, 151-60 (2006).
Vaughn, Arthur H., Bull. Am. Astron. Soc. 35, 1454-55 (2003)


AIP Center for History of Physics
Caltech Archives (4 photos)
Huntington Library (many)

Named after him

Minor Planet #3

67 Babcock (with H.D. Babcock)


Papers, etc.

Papers from his directorship of the Mt. Wilson & Palomar Observatories are at the Huntington Library. Excellent introduction. 28,000 items in 89 boxes. The AIP Niels Bohr Library & Archives has 1975 and 1977 oral history interviews of Horace Babcock. There is an audiotape of a 1978 oral history interview at Caltech Archives.

Other References: Historical

Search ADS for works about Babcock

Babcock, Horace W., “Diffraction Gratings at the Mount Wilson Observatory,” Physics Today 39, 7, 34-42 (1986) or Vistas in Astronomy 29, 153 (1986).

Howard, R., “Eight Decades of Solar Research at Mt. Wilson,” Solar Physics 100, 171-187 (1985).

Hufbauer, Karl, Exploring the Sun: Solar Science Since Galileo (Johns Hopkins Univ. Press, Baltimore, 1991).

Sandage, AllanCentennial History of the Carnegie Institution of Washington. Vol. 1, The Mount Wilson Observatory: Breaking the Code of Cosmic Evolution (Cambridge Univ. Press, Cambridge, UK, 2004).

Vanderburgh, William L., “Putting a New Spin on Galaxies: Horace W. Babcock, the Andromeda Nebula, and the Dark Matter Revolution,’ Journal for the History of Astronomy 45, 141-60 (2014).

Other References: Scientific

Search ADS for works by Babcock

Babcock, Horace W., “The Paschen Series of Hydrogen Lines in the Spectrum of the Solar Chromosphere,” PASP 44, 323-24 (1932).

Babcock, Harold D. & Horace W. Babcock, “Some New Features of the Solar Spectrum,” PASP 46, 132-33 (1934).

Babcock, Horace W., “Recent Observations of Solar Chromospheric and Disk Spectra in the Infra-Red,” PASP 47, 321 (1935).

Babcock, Horace W., “The Rotation of the Andromeda Nebula,” Lick Obs. Bull. 498, 41-51 (1939).

Babcock, Horace W., “Test for a Magnetic Field in the White Dwarf 40 Eridani B,” PASP 60, 368-70 (1948) [reprinted in the Centennial Edition, PASP 100, 1299-1301 (1988), followed by a modern review by James Liebert, 1301-05.

Babcock, Horace W., “A Photoelectric Guider for Astronomical Telescopes,” Ap.J. 107, 73-77 (1948).

Babcock, Harold D. & Horace W. Babcock, “The Ruling of Diffraction Gratings at the Mount Wilson Observatory,” Journal of the Optical Society of America 41, 776-86 (1951).

Babcock, Horace W. & Harold D. Babcock, “Mapping the Magnetic Fields of the Sun,” PASP 64, 282-87 (1952).

Babcock, H.W., “The Possibility of Compensating Astronomical Seeing,” PASP 65, 229-36 (1953). [The first paper on adaptive optics.]

Babcock, Horace W., “The Solar Magnetograph,” Ap.J. 118, 387-96 (1953) [reprinted in the centennial edition Ap.J. 525, 525-36 (1999) with a modern commentary by William Livingston and also in Selected Papers on Instrumentation in Astronomy ed. by William Livingston & Brian J. Thompson (SPIE Optical Engineering Press, Bellingham, WA, 1993), p. 373].

Babcock, H.W. & Cowling, T. G., “General Magnetic Fields in the Sun and Stars (Report on Progress of Astronomy),” MNRAS 113, 357-81 (1953).

Simpson, J.A., H.W. Babcock, & H.D. Babcock, “Association of a ‘Unipolar’ Magnetic Region on the Sun with Changes of Primary Cosmic-Ray Intensity,” Phys. Rev. 98, 1402-06 (1955).

Babcock, Horace W., “Stellar Magnetic Fields,” in Bo Lehnert, ed., Electromagnetic Phenomena in Cosmical Physics, Proceedings from IAU Symposium no. 6 (Cambridge University Press, 1958), pp. 161-65.

Babcock, H.W. & H.D. Babcock, , “Photospheric Magnetic Fields,” in Bo Lehnert, ed., Electromagnetic Phenomena in Cosmical Physics, Proceedings from IAU Symposium no. 6 (Cambridge University Press, 1958), pp. 239-47.

Babcock, H.W., “The Topology of the Sun’s Magnetic Field and the 22-Year Cycle,” Ap.J. 133, 572-87 (1961).

Babcock, Horace W., “Control of a Ruling Engine by a Modulated Interferometer,” Applied Optics 1, 415-20 (1962).

Babcock, H.W., “The Sun’s Magnetic Field,” Ann. Rev. Astron. Astrophys. 1, 41-58 (1963).

Hardy, John W., Adaptive Optics for Astronomical Telescopes (Oxford Univ. Press, Oxford, 1998).

Other Works: Popularizations, History, etc.

Babcock, Horace W., “Optical Astronomy in Perspective,” Astronomical Society of the Pacific Leaflets 10, 89-96 (1967) [Leaflet #462, excerpted from Science 156, 1317-22 (1967).