This unnamed lunar feature has had many names, including Mons Undset after the 1928 Nobel Prize winner Sigrid Undset.
An Apollo 15 image of Lambert Crater with Mons Undset to the west (right, where we added a circle) casting a pyramidal shadow. Mons Undset is named after the novelist Sigrid Undset. Credit: NASA.
On the night of September 23, 2023, I was focusing my 3-inch Tele Vue refractor on the Moon to capture the sunrise over Lambert Crater when a bright pyramid of light just east of the crater caught my attention. This isolated peak was the brightest feature to emerge from the lunar twilight that night. At high power, the sharply cut facets of the mountain reflected the rays of the rising sun in the most attractive manner. I immediately had to know the name of the mountain, only to discover… it doesn't have one.
But he did it once! I'll explain it.
The next morning, I checked NASA's online information. Scientific Visualization Studio Moon Phase and Libration (which shows the Moon on any chosen date with countless labels), as well as the ACT-REACT QuickMap Lunar Reconnaissance Orbiter Camera, but neither site identified this peak. The mountain was also not listed in the International Astronomical Union's (IAU) Gazetteer of Planetary Nomenclature of the Moon.
Doubting that such a brilliant feature was unnamed, I went back in time to the 1913 Compiled List of Lunar Formations. Approved by the International Association of Academies, this work was the first attempt to remedy the unsatisfactory state of lunar nomenclature of the day. . (At the time, the Moon's most prominent features were known by at least three different names, depending on the source.) It did not disappoint: The Collated List provides us with the first official mention of the name of our target mountain: Lambert Gamma (Γ ).
german astronomer Johann Henrich Mädler He assigned that name to the mountain in his and Wilhelm Beer's work. Selenographic Map (1836), which was then the universally accepted standard in selenography. Mädler's convention was to name isolated lunar peaks with the name of a nearby crater followed by a Greek letter. In his 1876 book The Moon and the conditions and configurations of its surface.Edmund Neison gives a wonderful description of Lambert Γ: “Because of its curved shape, Mountain Γ…sometimes looks like a crater…Sometimes this peak shines very conspicuously on the terminator.”
Lambert's uppercase Gamma Γ was changed to lowercase Lambert γ in the Named Lunar Formations of 1935, the first official IAU nomenclature list. When the IAU discontinued the use of Greek letters for elevated elements in 1973, Lambert γ was renamed Mons Undset, after Sigrid Undseta Danish-born Norwegian novelist who won the Nobel Prize for Literature in 1928.
Unfortunately, when the name Undset was applied to its lunar mountain in the 1973 Lunar Topographic Orthophotomap Series (the first complete, continuous mapping based on photographs from Apollo 15, 16, and 17), its name was misspelled “Undest.” . Instead of correcting the mistake, the IAU stripped the mountain of its name, leaving it in nomenclature limbo.
Most current references lean toward unofficially renaming Lambert γ Mountain (see Astronomy Magazine Guide to the Moon .PDF here) but why take away an honor given to a great woman just because of a typo? (For what it's worth, in 1985 the IAU named a crater on Venus after Undset, but we can't visually admire this view.)
My observation of Mons Undset occurred at a lunar colonitude of 18.3°, which must have been one of the occasions mentioned by Neison, when the mountain appears as a striking site near the terminator. But Mons Undset is sometimes so unusual that observers have mistaken it for a transient lunar phenomenon. Therefore, it is a show worth following and remembering.
In his book Christmas and Twelfth Night, Undset writes: “Let us remember that He has given us the sun, the moon and the stars.” And so we don't forget, we gave him a mountain on the Moon. As always, send your opinions to sjomeara31@gmail.com.
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