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  • MPEC 2010-W10 : BRIAN MARSDEN (1937 Aug. 5-2010 Nov. 18)

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    M.P.E.C. 2010-W10                                Issued 2010 Nov. 18, 15:41 UT
    
         The Minor Planet Electronic Circulars contain information on unusual
             minor planets and routine data on comets.  They are published
       on behalf of Commission 20 of the International Astronomical Union by the
              Minor Planet Center, Smithsonian Astrophysical Observatory,
                              Cambridge, MA 02138, U.S.A.
    
             Supported in part by the Steven and Michele Kirsch Foundation
                 Prepared using the Tamkin Foundation Computer Network
    
                                  MPC@CFA.HARVARD.EDU
              URL http://cfa-www.harvard.edu/iau/mpc.html  ISSN 1523-6714
    
                          BRIAN MARSDEN (1937 Aug. 5-2010 Nov. 18)
    
       Brian Geoffrey Marsden was born on 1937 August 5 in Cambridge, England. His
    father, Thomas, was the senior mathematics teacher at a local high school.  It
    was his mother, Eileen (nee West), however, who introduced him to the study
    of astronomy, when he returned home on the Thursday during his first week in
    primary school in 1942 and found her sitting in the back yard watching an
    eclipse of the sun.  Using now frowned-upon candle-smoked glass, they
    sat watching the changing bite out of the sun.  What most impressed the budding
    astronomer, however, was not that the eclipse could be seen, but the fact that
    it had been predicted in advance, and it was the idea that one could make
    successful predictions of events in the sky that eventually led him to his
    career.
    
       When, at the age of 11, he entered the Perse School in Cambridge he was
    developing primitive methods for calculating the positions of the planets.
    He soon realized that earlier astronomers had come up with more accurate
    procedures for doing this over the centuries, and during the next couple of
    years this led to his introduction to the library of the Cambridge University
    Observatories and his study of how eclipses, for example, could be precisely
    computed.  Together with a couple of other students he formed a school
    Astronomical Society, of which he served as the secretary.  At the age of 16 he
    joined and began regularly attending the monthly London meetings of the British
    Astronomical Association.  He quickly became involved with the Association's
    Computing Section, which was known specifically for making astronomical
    predictions other than those that were routinely being prepared by professional
    astronomers for publication in almanacs around the world.  Under the watchful
    eyes of the director and assistant director of the Computing Section, this led
    him to prepare and publish predictions of the occasions when one of Jupiter's
    moons could be seen to pass directly in front of another.  He also calculated
    the gravitational effects of the planets on the dates and sky positions of
    the returns of some periodic comets.  He carried out these computations using
    seven-place logarithms.  After all, this was long before pocket calculators had
    been invented, and the construction of large electronic computers was still
    then very much in its infancy.  He always maintained that making such
    computations by primitive means significantly increased one's understanding of
    the science involved.  During his last year of high school he also became a
    junior member of the Royal Astronomical Society.
    
       He was an undergraduate at New College, University of Oxford.  In his first
    year there he persuaded the British Astronomical Association to lend him a
    mechanical calculating machine, allowing him thereby to increase his
    computational productivity.  By the time he received his undergraduate degree,
    in mathematics, he had already developed somewhat of an international
    reputation for the computation of orbits of comets, including new discoveries.
    He spent part of his first two undergraduate summer vacations working at
    the British Nautical Almanac Office.  He also responded to an inquiry from
    Dorothy L. Sayers involving the ancient Roman poet Lucan.  Incensed by what
    she perceived as grossly unfair criticism of Lucan by A. E. Housman and Robert
    Graves, she elicited his assistance during the last year of her life to
    support her view that Lucan's understanding of astronomy and geography was
    reasonably valid.  Dr. Sayers' extensive correspondence in the course of this
    study is included in the last volume of her collected letters.
    
       After Oxford, he took up an invitation to cross the pond and work at the Yale
    University Observatory.  He had originally planned to spend just a year there
    carrying out research on orbital mechanics, but on his arrival in 1959 he was
    also enrolled as a Yale graduate student.  With the ready availability of the
    university's IBM 650 computer in the observatory building, he had soon
    programmed it to compute the orbits of comets.  Recalling his earlier interest
    in Jupiter's moons, he completed the requirements for his Ph.D. degree with a
    thesis on "The Motions of the Galilean Satellites of Jupiter".
    
       At the invitation of director Fred Whipple, he joined the staff of the
    Smithsonian Astrophysical Observatory in Cambridge (MA) in 1965.  Dr. Whipple
    was probably best known for devising the "dirty snowball" model for the nucleus
    of a comet a decade and a half earlier.  At that time there was only rather
    limited evidence that the motion of a comet was affected by forces over and
    above those of gravitation (limited because of the need to compute the orbit by
    hand), and the Whipple model had it that those forces were due to the comet's
    reaction to vaporization of the cometary snow or ice by solar radiation.  Dr.
    Marsden therefore developed a way to incorporate such forces directly into the
    equations that governed the motion of a comet.  Application of a computer
    program that included these nongravitational effects to several comets soon
    gave results that were nicely compatible with Dr. Whipple's original idea.
    Continued refinement of the nongravitational terms, much of it done in
    collaboration with Zdenek Sekanina, a Czech astronomer and friend of
    Dr. Marsden whom he and Dr. Whipple succeeded in bringing to the U.S. as a
    refugee following the Soviet invasion of Prague in 1968, resulted in a wealth
    of improved computations of cometary orbits by the time Dr. Sekanina moved to
    California in 1980.  It is noteworthy that the procedure devised and developed
    by Dr. Marsden is still widely used to compute the nongravitational effects of
    comets, with relatively little further modification by other astronomers.
    
       The involvement of the Smithsonian Astrophysical Observatory with comets had
    been given a boost, shortly before Dr. Marsden's arrival there, by the
    transfer there from Copenhagen of the office of the Central Bureau for
    Astronomical Telegrams, a quaintly named organization that was established by
    the International Astronomical Union soon after its founding in 1920.  The
    CBAT is responsible for disseminating information worldwide about the
    discoveries of comets, novae, supernovae and other objects of generally
    transient astronomical interest.  It is the CBAT that actually names the
    comets (generally for their discoverers), and it has also been a repository
    for the observations of comets to which orbit computations need to be fitted.
    Dr. Marsden succeeded Dr. Owen Gingerich as the CBAT director in 1968.  He was
    joined by Daniel Green as a student assistant a decade later, and Dr. Green
    took over as CBAT director in 2000.  Until the early 1980s the Bureau really
    did receive and disseminate the discovery information by telegram (with
    dissemination also by postcard Circular), although e-mail announcements then
    understandably began to take over.  The last time the CBAT received a telegram
    was when Thomas Bopp sent word of his discovery of a comet in 1995.  Since
    word of this same discovery had already been received from Alan Hale a few
    hours earlier by e-mail, the object was very nearly just named Comet Hale,
    rather than the famous Comet Hale-Bopp that beautifully graced the world's
    skies for several weeks two years later.
    
       The comet prediction of which he was most proud was of the return of comet
    Swift-Tuttle, which is the comet associated with the Perseid meteors each
    August.  It had been discovered in 1862, and the conventional wisdom was that
    it would return around 1981.  He followed that line for much of a paper he
    published on the subject in 1973.  He 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, and this comet has the longest orbital
    period of all the comets whose returns have been successfully predicted.
    
       Although the CBAT also traditionally made announcements of the discoveries
    of asteroids that came close to the earth, the official organization for
    attending to discoveries of asteroids (more than 99% of which are located in
    a belt between Mars and Jupiter) is the Minor Planet Center.  Also operated
    by the International Astronomical Union, the MPC was located until 1978 at the
    Cincinnati Observatory.  In that year the director, Dr. Paul Herget, was
    retiring, and it was necessary for the Center to find a new home.  Accordingly,
    the IAU asked Dr. Marsden also to take over the direction of the MPC.  Thanks
    to the transfer of associate director Conrad Bardwell with the MPC records
    from Cincinnati, this task was rendered easier.  While the CBAT and the MPC
    still maintained their separate entities, there was a lot of common ground
    between them.  Dr. Marsden was therefore able to introduce some efficiencies
    into their combined operation.  On Mr. Bardwell's retirement at the end of
    1989, Gareth Williams joined the MPC staff and later became associate director.
    
       The advances in electronic communication during the 1990s also permitted
    improvements in MPC operation. Perhaps the most important of these was the
    development, in 1996, of the Internet "Near-Earth Object Confirmation Page".
    This draws attention to candidate earth-approaching objects in need of
    follow-up observations as soon as they have been reported to the MPC,
    following the derivation by Dr. Marsden of a particularly ingenious method
    for estimating the uncertainty of the prediction by automatically computing a
    series of orbits that represent just the first and the last observations.  In
    1998 he developed a certain amount of notoriety by suggesting that an object
    called 1997 XF11 could collide with the earth.  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.  Without those 1990
    observations, however, the object's orbit would have become very uncertain
    following a close to moderate approach to the earth in 2028; indeed, Dr.
    Marsden correctly demonstrated that there was the possibility of an earth
    impact in 2040 and in several neighboring years.  He was thereby able
    eventually to persuade his principal critics routinely to perform similar
    uncertainty computations for all near-earth objects as they were announced.
    Again, as more data accrue, it is almost certain to happen that all possible
    impacts with moderately large objects (i.e., those at least several hundred
    feet across) during the next century, say, will disappear.  While the
    production of such computations was directly due to his encouragement, it was
    always with some amusement that he saw cases where further data forced his
    former critics sheepishly to withdraw their earlier frightening statements
    about a potentially dangerous object.
    
       Dr. Marsden was particularly fascinated by the appearance of a group of
    comets that passed close to the sun.  Known as members of the Kreutz group,
    after a German astronomer who studied them in the late nineteenth century, the
    discovery of three more of these sungrazing comets in the mid-twentieth
    century led him to undertake a detailed examination of how the individual
    comets may have evolved from each other.  He published this examination in
    1967, following it up with a further study in 1989 involving a more recent
    bright Kreutz comet, as well as several much fainter objects that had been
    detected from sun-observing coronagraphs out in space.  Beginning in 1996,
    these were being found by the SOHO coronagraphs at rates ranging from a few
    dozen to more than one hundred per year.  Unfortunately, the faintness of the
    comets and the poor accuracy with which they could be measured made it
    difficult to establish their orbits as satisfactorily as Dr. Marsden would
    have liked. More significantly, however, he was able to recognize that the
    SOHO data also contained another group of comets with similar orbits, these
    comets now known as members of the "Marsden group".  Unlike the individual
    Kreutz comets, which have orbital periods of several centuries, it seems that
    the Marsden comets have orbital periods of only five or six years, leading
    him to try and recognize the same object at different passages near the
    sun and thereby predict future returns.  Two other well-populated groups have
    also been detected in the SOHO data.
    
       Another series of astronomical discoveries that greatly interested him were
    what he always called the "transneptunian objects", although many of his
    colleagues have insisted on calling them "objects in the Kuiper Belt".  When
    what those same colleagues considered to be the first of these was discovered
    in 1992, Dr. Marsden immediately remarked that this was untrue, because Pluto,
    discovered in 1930 and admittedly somewhat larger in size, had to be the
    first.  More specifically, he was the first to suggest, correctly, that three
    further transneptunian objects discovered in 1993 were exactly like Pluto in
    the sense that they all orbit the sun twice while Neptune orbits it thrice.
    This particular recognition set him firmly on the quest to "demote" Pluto.
    Success required the discovery of transneptunian objects more comparable to
    Pluto in size, something that finally happened in 2005 with the discovery of
    the object that came to be known as Eris.  At its triennial meeting in 2006
    in Prague, the IAU voted to designate these objects, together with two
    further transneptunian objects now known as Makemake and Haumea, as well as
    the largest asteroid, Ceres, members of a new class of "dwarf planet".
    
       It was also at the IAU meeting in Prague that Dr. Marsden stepped down as MPC
    director, and he was quite entertained by the thought that both he and Pluto
    had been retired on the same day.  While he remained working at the MPC (and
    also the CBAT) in an emeritus capacity, the directorship was passed to
    Dr. Timothy Spahr, whom he had brought to the MPC in 2000.
    
       Dr. Marsden served as an associate director of the Harvard-Smithsonian Center
    for Astrophysics (the combination of the Smithsonian Astrophysical Observatory
    and the Harvard College Observatory) for 15.75 years from the beginning of 1987
    (the longest tenure for any of the Center's associate directors).  He was chair
    of the Division of Dynamical Astronomy of the American Astronomical Society
    during 1976-1978 and president of the IAU commissions that oversaw the
    operation of the minor Planet Center (1976-1979) and the Central Bureau for
    Astronomical Telegrams (2000-2003).  He continued to serve subsequently on the
    two solar-system nomenclature committees of the IAU, being the perennial
    secretary of the one that decides on names for asteroids.  He also continued
    to publish a "Catalogue of Cometary Orbits", the first of these having
    appeared in 1972 and its successors roughly at intervals of two years.
    
       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) of the 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 1964
    December 26, and fathered Cynthia (who is married to Gareth Williams,
    still MPC associate director), of Arlington, Massachusetts; and Jonathan,
    of San Mateo, California.  There are three Californian grandchildren,
    Nikhilas, Nathaniel and Neena.  A sister, Sylvia Custerson, continues to reside
    in Cambridge, England.
    
    Gareth V. Williams           (C) Copyright 2010 MPC           M.P.E.C. 2010-W10
    

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