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Brian Marsden, Eminent Astronomer and Comet/Asteroid Tracker, Dies

November 19, 2010

Dr. Brian Geoffrey Marsden passed away Thursday, Nov. 18 at the age of 73 following a prolonged illness. He was a Supervisory Astronomer at the Smithsonian Astrophysical Observatory and Director Emeritus of the Minor Planet Center.

“Brian was one of the most influential comet investigators of the twentieth century,” said Charles Alcock, Director of the Harvard-Smithsonian Center for Astrophysics, “and definitely one of the most colorful!”

Dr. Marsden specialized in celestial mechanics and astrometry, collecting data on the positions of asteroids and comets and computing their orbits, often from minimal observational information. Such calculations are critical for tracking potentially Earth-threatening objects. The New York Times once described Marsden as a “Cheery Herald of Fear.”

The comet prediction of which Marsden was most proud was that of the return of Comet Swift-Tuttle, which is the comet associated with the Perseid meteor shower each August. Swift-Tuttle had been discovered in 1862, and the conventional wisdom was that it would return around 1981. Marsden had a strong suspicion, however, that the 1862 comet was identical with one seen in 1737, and this assumption allowed him to predict that Swift-Tuttle would not return until late 1992. This prediction proved to be correct. This comet has the longest orbital period of all the comets whose returns have been successfully predicted.

In 1998, Marsden developed a certain amount of notoriety by suggesting that an object called 1997 XF11 could collide with Earth. He said that he did this as a last-ditch effort to encourage the acquisition of further observations, including searches for possible data from several years earlier. The recognition of some observations from 1990 made it quite clear that there could be no collision with 1997 XF11 during the foreseeable future.

Dr. Marsden also played a key role in the “demotion” of Pluto to dwarf planet status. He once proposed that Pluto should be cross-listed as both a planet and a “minor planet,” and assigned the asteroid number 10000. That proposal was not accepted. However, in 2006 a vote by members of the International Astronomical Union created a new category of “dwarf planets,” which includes Pluto, Ceres, and several other objects. Pluto was designated minor planet 134340. This decision remains controversial.

Marsden was born on August 5, 1937, in Cambridge, England. He received an undergraduate degree in mathematics from New College, University of Oxford, and a Ph.D. from Yale University.

At the invitation of director Fred Whipple, Dr. Marsden joined the staff of the Smithsonian Astrophysical Observatory in Cambridge, Mass., in 1965. He became director of the Minor Planet Center in 1978. (The MPC is the official organization in charge of collecting observational data for asteroids and comets, calculating their orbits, and publishing this information via Circulars.) Marsden served as an associate director of the Harvard-Smithsonian Center for Astrophysics from 1987 to 2003 (the longest tenure of any of the Center’s associate directors).

Among the various awards he received from the U.S., the U.K., and a handful of other European countries, the ones he particularly appreciated were the 1995 Dirk Brouwer Award (named for his mentor at Yale) from the American Astronomical Society’s (AAS) Division on Dynamical Astronomy, and the 1989 Van Biesbroeck Award (named for an old friend and observer of comets and double stars), then presented by the University of Arizona (now by the AAS) for service to astronomy.

Dr. Marsden married Nancy Lou Zissell, of Trumbull, Connecticut, on December 26, 1964, and fathered Cynthia Louise Marsden-Williams (who is now married to Gareth Williams, still MPC associate director), of Arlington, Massachusetts, and Jonathan Brian Marsden, of San Mateo, California. He also has three grandchildren in California: Nikhilas, Nathaniel, and Neena. A sister, Sylvia Custerson, continues to reside in Cambridge, England.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Image Caption: Dr. Brian Marsden. Credit: Harold Dorwin

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