Plummer Crater Honors British Astronomer Henry Crozier Keating Plummer

Summary: Plummer Crater honors British astronomer Henry Crozier Keating Plummer, the last Royal Astronomer of Ireland and formulator of the Plummer model.

Detail of Lunar Astronautical Chart (LAC) 105 shows the Plummer Crater system, north of gigantic Apollo Crater, in the lunar far side’s southeastern quadrant; courtesy NASA (National Aeronautics and Space Administration) / GSFC (Goddard Space Flight Center) / ASU (Arizona State University): U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature

Plummer Crater honors British astronomer Henry Crozier Keating Plummer, the last Royal Astronomer of Ireland, whose astronomical contributions include formulating the Plummer model for globular clusters.

Plummer Crater is a lunar impact crater in the far side’s southeastern quadrant. Larger and smaller impact craters gouge Plummer’s worn rim. Tiny craterlets dot Plummer’s interior floor. A central peak rises to the east of the crater’s midpoint.

Plummer Crater is centered at minus 24.62 degrees south latitude, minus 154.86 degrees west longitude, according to the International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature. The southern hemisphere crater records northernmost and southernmost latitudes of minus 23.38 degrees south and minus 25.87 degrees south, respectively. It registers easternmost and westernmost longitudes of minus 153.48 degrees west and minus 156.23 degrees west. Plummer Crater’s diameter measures 75.7 kilometers.

Plummer Crater parents five satellites. Two satellites (C, W) claim northern positions with respect to their parent. Three satellites (M, N, R) assume southern placements with respect to their parent.

The Plummer Crater system resides in the lunar far side’s equatorial and middle latitudes, to the north of gigantic Apollo Crater. Apollo’s name honors the National Aeronautics and Space Administration’s (NASA) Apollo program. Project Apollo achieved six crewed lunar landings.

Apollo Crater is centered at minus 35.69 degrees south latitude, minus 151.48 degrees west longitude. The middle latitude crater’s northernmost and southernmost latitudes stretch from minus 28.12 degrees south to minus 44.19 degrees south, respectively. Its easternmost and westernmost longitudes reach minus 140.58 degrees west and minus 162.07 degrees west, respectively. Apollo Crater’s diameter spans 524.23 kilometers.

Plummer Crater honors British astronomer Henry Crozier Keating Plummer (Oct. 24, 1875-Sept. 30, 1946). The International Astronomical Union (IAU) approved Plummer as the crater’s official name in 1970, during the organization’s XIVth (14th) General Assembly, held from Aug. 18, to Aug. 27, in Brighton, United Kingdom. Before its formal naming, Plummer Crater was designated as Crater 384. The letter designations for the Plummer Crater system’s five satellites were approved in 2006.

In 1901, Plummer was appointed as Second Assistant at the Radcliffe Observatory, Oxford. His father, William Edward Plummer (March 26, 1849-May 22, 1928), had held the position of first assistant at Oxford University’s observatory from 1874 to 1892.

Plummer published “The Positions of 70 Stars in the Cluster M13 Herculis” in the November 1904 issue of the Monthly Notices of the Royal Astronomical Society. In his biography of Plummer for the May 1948 issue of Biographical Memoirs of the Royal Society, British stellar spectrophotometrist William Michael Herbert Greaves (Sept. 10, 1897-Dec. 24, 1955) described the paper as foreshadowing the Radcliffe Observatory second assistant’s contribution, seven years later, to globular cluster research.

Plummer expounded his globular cluster density law, now known as the Plummer model or Plummer sphere, in the March 1911 issue of the Monthly Notices of the Royal Astronomical Society. His paper, “On the Problem of Distribution in Globular Star Clusters,” considered four globular clusters: Omega Centauri (ω Centauri, Omega Centauri; Omega Cen, ω Cen; NGC 5139)Cen; NGC 5139), 47 Tucanae (47 Tuc; NGC 104), Messier 13 (M13; NGC 6205; Hercules Cluster) and Messier 3 (M3; NGC 5272).

In 1912 Plummer accepted appointment as the Andrews Professor of Astronomy at the University of Dublin’s Trinity College Dublin in eastern coastal Ireland. The Andrews chairship entailed associated titles as the director of Dunsink Observatory and as the Royal Astronomer for Ireland. Plummer was the ninth and last holder of the Andrews Chair and the eighth and last holder of the title of Royal Astronomer for Ireland.

In addition to a steady output of observational, analytical papers from Ireland, Plummer published, in 1918, his textbook on motion and gravity, An Introductory Treatise on Dynamical Astronomy. He stated in his preface that he intended the treatise as “instructive to the reader whose studies in this branch go no further” and as helpful in elucidating “more easily the technical details to be met with in more special treatises” (page vi). Plummer explained: “A distinct effort has been made to leave no formulae in a shape unsuitable for translation into numbers.”

On May 13, 1920, Plummer was elected a Fellow of The Royal Society (FRS). The Royal Society’s fellowship record for Plummer notes his authorship of 68 papers on “Astronomical or Mathematical subjects,” with the Monthly Notices of the Royal Astronomical Society as the chief publisher.

In 1921, Plummer accepted the Chair of Mathematics at the Artillery College (renamed Military College of Science in 1927) in southeast London’s Woolwich district. He retained the position until his retirement in 1940.

Henry Crozier Keating Plummer was elected in 1939 as the 51st president of the Royal Astronomical Society (RAS). He gave three presidential addresses during his two-year term.

The takeaways for Plummer Crater, which honors British astronomer Henry Crozier Keating Plummer, are that the far side crater occupies equatorial and middle latitudes in the southeastern quadrant, to the north of enormous Apollo Crater; that Plummer parents five satellites; and that the Plummer Crater system’s namesake, who was the last Royal Astronomer for Ireland, formulated his globular cluster distribution of mass law, now known as the Plummer model or Plummer sphere, in 1911; and that he published a textbook on motion and gravity, An Introductory Treatise on Dynamical Astronomy, in 1918.

Detail of Shaded Relief and Color-Coded Topography Map shows Plummer Crater, north of Apollo Crater, in the lunar far side’s southeastern quadrant: U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

Detail of Lunar Astronautical Chart (LAC) 105 shows the Plummer Crater system, north of gigantic Apollo Crater, in the lunar far side’s southeastern quadrant; courtesy NASA (National Aeronautics and Space Administration) / GSFC (Goddard Space Flight Center) / ASU (Arizona State University): U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/Lunar/lac105_wac.pdf

Detail of Shaded Relief and Color-Coded Topography Map shows Plummer Crater, north of Apollo Crater, in the lunar far side’s southeastern quadrant: U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/moon_farside.pdf

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