Edwin Hubble’s Doctoral Thesis: Using OCHRE to Associate Interdisciplinary Materials

Edwin Hubble’s PhD research in 1916 concerned exploring properties of faint nebulae recorded photographically with George Ritchey’s 24-inch reflector telescope at Yerkes Observatory. A thorough investigation of Hubble’s dissertation and research methods — his measurements of the size distribution, morphologies, and clustering properties of the nebulae — yields insight into Hubble’s early thoughts on the nature of the faint nebulae, and thus context for his later work in these fields. Hubble’s measurements were made visually on an x-y stage and recorded in detailed tables in his dissertation. The tables include 588 nebulae with (RA, Dec) and size, brightness, and morphological information. Our transcriptions of these tables enable cross-identification and other studies. We have also digitized a series of Hubble’s original photographic plates: two from each of his seven high-latitude fields, and a pair of plates of the Perseus Cluster that he used for calibration. These fields cover 3 square degrees and reach B ~19, a competitive combination for the time. Our digitizations yield a precision of about 0.1 mag for stellar sources. The FITS headers include metadata from the original logbooks as well as our World Coordinate System solution. Pairing Hubble’s annotations on the glass plates with comments in his data tables enables a more comprehensive understanding of his work, supported by Hubble’s correspondence with Edwin Frost, Director of Yerkes Observatory and Hubble’s thesis advisor. These files — the transcribed tables and letters, as well as the digitized renderings of Hubble’s plates — are being made accessible via a versatile graph database called OCHRE (Online Cultural and Historical Research Environment). OCHRE provides a highly flexible way to explore and extend this material, for example by facilitating connections between individual items (the glass plates and their corresponding entries in the logbooks, for example). In this presentation we give examples of how these data can be used for time-domain research by pairing with modern catalogs. We also give examples of how OCHRE provides a platform for historical research, and finally we indicate some ideas for astronomy instruction.