Summary: Merrill Crater honors American astronomer Paul Willard Merrill, who defined a new spectral class, S-type stars, through his specialty in spectroscopy.
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| Detail of Lunar Astronautical Chart (LAC) 9 shows Merrill Crater (center left) as a far side north polar region crater, with nearest named neighbors Froelich M, to the northeast, and the Niepce Crater system to the south, respectively; 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 |
Merrill Crater honors American astronomer Paul Willard Merrill, whose accomplishments included spectroscopic scrutiny of classes of stars with peculiar spectra (light’s wavelengths).
Merrill is an impact crater in the lunar far side’s high northern latitudes. Merrill has a worn rim and a relatively level interior floor.
Merrill is centered at 74.83 degrees north latitude, minus 117.45 degrees west longitude, according to the International Astronomical Union’s (IAU) Gazetteer of Planetary Nomenclature. The north polar crater obtains northernmost and southernmost latitudes at 75.77 degrees north and 73.89 degrees north, respectively. Its easternmost and westernmost longitudes occur at minus 113.85 degrees west and minus 121.04 degrees west, respectively. Merrill Crater’s diameter spans 56.99 kilometers.
Merrill Crater parents two satellites. Merrill X and Merrill Y merge into a dual-lobed formation that connects with their parent’s northern rim.
Merrill X occurs as the Merrill Crater system’s most northerly and most westerly component. The satellite converges with western Merrill Y.
Merrill X is centered at 76.7 degrees north latitude, minus 120.67 degrees west longitude. It posts northernmost and southernmost latitudes of 77.16 degrees north and 76.24 degrees north, respectively. Satellite X marks easternmost and westernmost longitudes at minus 118.68 degrees west and minus 122.66 degrees west, respectively. Merrill X’s diameter of 27.71 kilometers places it as the smaller of the Merrill Crater system’s two satellites and as the Merrill Crater system’s smallest component.
Merrill Y resides as an intermediary between conjoined Merrill X and the Merrill Crater system’s primary crater. Southern Merrill Y attaches to its parent’s northern rim; Merrill Y’s western perimeter opens into eastern Merrill X.
Merrill Y is centered at 76.33 degrees north latitude, minus 117.94 degrees west longitude. Its northernmost and southernmost latitudes extend to 77.04 degrees north and 75.62 degrees north, respectively. Satellite Y’s easternmost and westernmost longitudes reach minus 114.94 degrees west and minus 120.94 degrees west, respectively. Merrill Y’s diameter of 42.96 qualifies it as the larger of the Merrill Crater system’s two satellites and as the Merrill Crater system’s second largest component.
Froelich M is the Merrill Crater system’s nearest named northern neighbor. Froelich M lies to the northeast of the Merrill Crater system’s conjoined satellites.
Froelich M is a solitary satellite in the Froelich Crater system. It resides north of its parent. The Froelich Crater system lies just beyond the lunar near side’s north-northwestern limb.
Froelich M is centered at 77.32 degrees north latitude, minus 110.87 degrees west longitude. It confines its northernmost and southernmost latitudes to 77.82 degrees north and 76.82 degrees north, respectively. It establishes easternmost and westernmost longitudes of minus 108.61 degrees west and minus 113.13 degrees west, respectively. Froelich M has a diameter of 30.1 kilometers.
The Niepce Crater system is the Merrill Crater system’s nearest named southern neighbors. Niepce Crater and its solitary satellite, Niepce F, lie to the south-southwest and south-southeast of Merrill Crater.
Niepce Crater is centered at 72.2 degrees north latitude, minus 120.15 west longitude. The worn primary crater records northernmost and southernmost latitudes of 73.18 degrees north and 71.21 degrees north, respectively. It registers easternmost and westernmost longitudes of minus 116.93 degrees west and minus 123.37 degrees west, respectively. Niepce Crater measures 59.69 kilometers.
Western Niepce F attaches to its parent’s eastern rim. It is centered at 72.13 degrees north latitude, minus 114.27 degrees west longitude. Niepce F finds northernmost and southernmost latitudes at 72.93 degrees north and 71.33 degrees north, respectively. Its easternmost and westernmost longitudes are obtained at minus 111.66 degrees west and minus 116.88 degrees west, respectively. Niepce F has a diameter of 48.55 kilometers.
Merrill Crater honors American astronomer Paul Willard Merrill (Aug. 15, 1887-July 19, 1961). The International Astronomical Union (IAU) approved Merrill as the crater’s official name in 1970, during the organization’s XIVth (14th) General Assembly, held in Brighton, United Kingdom, from Tuesday, Aug. 18, to Thursday, Aug. 27.
Merrill’s interest in observational astronomy informed his specialization in spectroscopy. As a stellar spectroscopist, he explored the physical properties of stars via dispersion of the stellar light into component wavelengths. In particular, Merrill focused on classes of stars with peculiar spectra (light’s wavelengths).
Merrill is credited with defining the class of S-type stars, also known as S stars. He discovered the presence of technetium (chemical symbol Tc; atomic number 43) in S-type stars. Technetium is an element without any known stable isotopes.
Paul Willard Merrill joined the staff of the Mount Wilson Observatory in 1919. His presence at the observatory did not end with his retirement in September 1962. In the National Academy of Sciences Biographical Memoirs for 1964, stellar spectroscopist Olin Chaddock Wilson (Jan. 13, 1909-July 13, 1994) described Merrill’s retirement as “. . . something of a joke among his associates” (page 246) because he continued his daily schedule of “long hours in his office” (page 246).
The takeaways for Merrill Crater, which honors American astronomer Paul Willard Merrill, are that the lunar impact crater lies in the far side’s high polar latitudes; that Merrill Crater parents two conjoined satellites, Merrill X and Merrill Y; that the crater’s namesake indulged his interest in observational astronomy through spectroscopy, which examines stellar spectra; and that his particular preference for non-normal stars motivated his scrutiny of S-type stars, which he is credited with defining.
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| Detail of Shaded Relief and Color-Coded Topography Map shows Merrill Crater as a far side north polar region occupant: 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:
Image credits:
Detail of Lunar Astronautical Chart (LAC) 9 shows Merrill Crater (center left) as a far side north polar region crater, with nearest named neighbors Froelich M, to the northeast, and the Niepce Crater system to the south, respectively; 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/lac_9_wac.pdf
Detail of Shaded Relief and Color-Coded Topography Map shows Merrill Crater as a far side north polar region occupant: U.S. Geological Survey, Public Domain, via USGS Astrogeology Science Center / Gazetteer of Planetary Nomenclature @ https://planetarynames.wr.usgs.gov/images/moon_np.pdf
For further information:
For further information:
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Available @ https://planetarynames.wr.usgs.gov/Feature/4627
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Available @ https://planetarynames.wr.usgs.gov/Feature/3860
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Available @ https://planetarynames.wr.usgs.gov/Feature/11353
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Available @ https://planetarynames.wr.usgs.gov/Feature/11354
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Available @ https://planetarynames.wr.usgs.gov/Feature/4257
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