Astronomy

Gray sky background with black dots that are stars. In the upper left corner, there is a significantly larger black dot (star), and at a 45º angle from it about halfway between the corner and the center of the plate, there is a black and gray galaxy which appears to have a spiral arm. — Galaxy M99 on glass plate 10B-1246

Photographed 1 April 1918

Black sky background with dots of white, red, yellow, and orange that are stars. In the upper left corner, there is a significantly larger red dot (star), and at a 45º angle from it about halfway between the corner and the center of the plate, there is a yellow-ish colored galaxy which appears to have a spiral arm. — SDSS image of Galaxy M99

Photographed c. 2000

New astronomical observations happen every minute of every day – terrestrial and space telescopes capture millions of pixels of data for scientists to use in research. This information grows our understanding of the universe exponentially.

But what about time domain astronomy, research focused on how astronomical objects and events vary over time? How can we “see” the sky as it was decades ago? Astronomical glass plates such as those in the Yerkes collection are treasure troves of historic observations and irreplaceable data, but they are also primarily analog, meaning they need to be digitized for contemporary scientific use.

The comparison of 100+ year-old and contemporary data isn’t apples to apples. It’s necessary to adjust and extrapolate during analysis. With support from a 12-month National Science Foundation Early-Concept Grant for Exploratory Research (AST-2101781), the UChicago team is researching, analyzing, and developing methods and procedures for using financially accessible equipment to digitize the glass plates in the Yerkes collection. Making the digitization process lower cost and accessible to all types of repositories helps to protect and preserve unique and irreplaceable observational archives and these data will be a valuable contribution to time domain astronomy, adding a wealth of primary source information to the history of astronomy.

What we're studying

Our team continues to explore digitization techniques. To date, we have focused on sky survey plates, and have done deep dives on two plates with different characteristics. The first, Ry60, was taken by George Ritchey in 1903 at Yerkes Observatory in Williams Bay, WI. This plate is 3.25 x 4.25" with the image outside of the galactic plane, allowing for the measurement of stars and extragalactic objects as well as providing a less-crowded field for analysis (although there are still 7,000 identified stars on the plate!) The second, 10B-161, was taken by E.E. Barnard in 1905 at Mount Wilson Observatory in Pasedena, CA in 1905. This plate is 12 x 12" and is included as Plate 8 in Barnard's publication, A Photographic Atlas of Selected Regions of the Milky Way (1927). As a photograph of the Milky Way, there are many more stars in the image (more than 100,000!) and is a good case study for testing our methods on more crowded fields.

A glass plate negative of Ry60. The background of the plate is gray, and the emulsion is peeling around all of the plate edges. Handwritten at the top of the plate is "Ry60 H.I 53 Pegasi." Handwritten at the bottom is Aug, 19, 03. Exp. 3h. 18" ap./Plate show. (Mess. ^ H.I) 53 Pegasi." The center of the plates is a slightly darker gray, with black stars throughout the field. Just left of center is M53, which is a small, fuzzy, vertical mark. — Ry60

A 12 by 12 inch glass plate negative. The background is gray, with the sky being a slightly darker gray. Handwritten at the top is "Sky da?? W 7h 0m-7h50m 1905 March 2..." Handwritten in the bottom left corner is "1905 March 22 7h 0m-7h50m #161". There are large black areas in the top right and bottom 2 corners. There is a red square drawn in the central 6 inches or so of the plate. The gray sky background is full of black stars. — 10B-161

The team has created astronomical data packages for each of these plates as well as published the methods and processes used for digitization and transformation necessary for contemporary astronomical research:

Astronomical data package for 10B-161

Astronomical data package for Ry60

Isaiah Escapa, Rowen Glusman, and Rachel Kovach-Fuentes, presenters. A Comparative Analysis of Glass Plate Digitization Methods: Methods Motivated by Stellar Variability. Midstates Consortium for Math and Science 2022 Undergraduate Research Symposium in the Physical Sciences, Math, and Computer Science, Nov. 2022

Glusman, et al, Digitization, Measurement, and Analysis of a 1905 Barnard Atlas Photographic Plate, Publications of the Astronomical Society of the Pacific, Volume 134, Number 1039

Isaiah Escapa and Audrey Scott, presenters. Photometric Analysis of a 1905 Photographic Plate. Midstates Consortium for Math and Science 2021 Undergraduate Research Symposium in the Physical Sciences, Math, and Computer Science, Nov. 2021

Cerny, et al, Precise Photometric Measurements from a 1903 Photographic Plate Using a Commercial Scanner, Publications of the Astronomical Society of the Pacific, Volume 133, Number 1022

E. Medina , W. Cerny, Y. Liang, J. Lin, M. Martinez, B. Ogonor, J. Sanchez, Digitizing Hubble's Thesis Plates. AAS 235 Meeting Abstracts

B. Ogonor, W. Cerny, A. Chapman, R. Glusman, Y. Liang, J. Lin, M. Martinez, E. Medina, A. Muratore, and J. Sanchez, Photometry and Analysis of a Sample of Quasars on Archival Yerkes Observatory Photographic Plates. AAS236 Abstracts. Vol 52 Issue 3

For more information about the project, please contact us at yerkesplates@lib.uchicago.edu.

Support for this project comes from the National Science Foundation (Grant AST-2101781), University of Chicago College Innovation Fund, John Crerar Foundation, Kathleen and Howard Zar Science Library Fund, Institute on the Formation of Knowledge, and Yerkes Future Foundation.