900 Rosalinde (prov. designation: or ) is an elongated background asteroid from the inner regions of the asteroid belt, that has a mean-diameter of approximately . It was discovered on 10 August 1918, by astronomer Max Wolf at the Heidelberg-Königstuhl State Observatory in southwest Germany. The lengthy S/D-type asteroid has a rotation period of 16.6 hours. It was likely named after "Rosalinde", a character in the operetta Die Fledermaus by Johann Strauss II. Orbit and classification Rosalinde is a non-family asteroid of the main belt's background population when applying the hierarchical clustering method to its proper orbital elements. It orbits the Sun in the inner asteroid belt at a distance of 2.1–2.9 AU once every 3 years and 11 months (1,421 days; semi-major axis of 2.47 AU). Its orbit has an eccentricity of 0.16 and an inclination of 12° with respect to the ecliptic. The body's observation arc begins at Heidelberg-Königstuhl State Observatory with its official discovery observation on 10 August 1918. Naming This minor planet was probably named after the character "Rosalinde", Eisenstein's wife, in the operetta Die Fledermaus by Johann Strauss II (1825–1899), after whom 4559 Strauss was named. Rosalinde's maid in the operetta, "Adele", is likely the namesake chosen by Wolf for another asteroid, 812 Adele. Lutz Schmadel, the author of the Dictionary of Minor Planet Names learned about the discoverer's source of inspiration from private communications with Dutch astronomer Ingrid van Houten-Groeneveld, who worked as a young astronomer at the discovering Heidelberg Observatory. Physical characteristics Rosalinde is an S-type/D-type in the SMASS-I spectral type-classification by Xu (1995), which surveyed and classified a total of 221 objects. However, Rosalindes classification, with its moderate albedo of 0.1 (see below) does not correspond to more modern taxonomies such as the Bus–Binzel SMASS classification (II), where the bright S-types and the dark D-types do not have intermediate albedos. Rotation period In June 2011, a rotational lightcurve of Rosalinde was obtained from photometric observations by Meaghann Stoelting and David DeGraffat at the Stull Observatory of the Alfred University in New York. Lightcurve analysis gave a rotation period of hours with a brightness variation of magnitude (). Assuming an equatorial view, the observers also constrained the object's elongated shape to be at least 36% longer than wide. The result supersedes a tentative period determination by French amateur astronomer René Roy from May 2007 (). Additional observation by the Spanish OBAS group gave