1421 Esperanto in the outer asteroid belt at a distance of 2.8–3.4 AU once every 5 years and 5 months (1,983 days; semi-major axis of 3.09 AU). Its orbit has an eccentricity of 0.08 and an inclination of 10° with respect to the ecliptic. The body's observation arc begins with its first observation as at Heidelberg Observatory in October 1906, almost 30 years prior to its official discovery observation at Turku. This minor planet was named by the discoverer after the artificial language, Esperanto, which was created by inventor and writer, Ludwik Lejzer Zamenhof (1859–1917), who used the pseudonym "Doktoro Esperanto". The
Ludwik Birkenmajer w przekładzie polskim" (1920) · Mikołaj Kopernik, "O obrotach ciał niebieskich i inne pisma" (2004) · Andrzej Śródka, "Uczeni polscy XIX-XX stulecia". Warszawa 1994, vol. I, p. 155-157 . Paweł Tarasiewicz, Zbigniew Pańpuch, "Birkenmajer Ludwik Antoni", "Powszechna encyklopedia filozofii" vol. I, Lublin 2000 · Władysław Horbacki, "Ludwik Antoni Birkenmajer (1855-1929)". Łódź 1930 Ludwik Birkenmajer Ludwik Antoni Birkenmajer (18 May 1855 - 20 November 1929), Polish historian of science, physicist, astronomer, professor of the Jagiellonian University. Descended from the German family settled in Galicia (Southern Poland) during the time of the Napoleon wars, later a part of the Austrian Habsburg Empire.