Lost Star Catalog of Hipparchus Uncovered with Advanced X-ray Technology

Researchers have utilized advanced X-ray fluorescence technology to uncover fragments of a previously lost star catalog, believed to have been created by the ancient Greek astronomer Hipparchus over 2,000 years ago. This discovery, made from a 1,500-year-old palimpsest manuscript, provides direct evidence of his astronomical observations and offers new insights into the history of science.

Fragments of a 2,000-year-old lost star catalog by ancient Greek astronomer Hipparchus have been uncovered using advanced X-ray fluorescence technology, providing direct evidence of his observations.

Unveiling the Codex Climaci Rescriptus

The manuscript, known as the Codex Climaci Rescriptus, is an animal-skin parchment currently held by the Museum of the Bible in Washington, D.C. In the 6th and 7th centuries, monks erased the original Greek astronomical texts from the parchment to overwrite them with Syriac translations of works by St. John Climacus. While the religious text has been visible for centuries, the underlying ancient Greek star coordinates and notes related to Hipparchus's work remained hidden.

A close analysis in 2022 first suggested the presence of an ancient star map, linking references to Earth's precession to Hipparchus's active period.

X-ray Fluorescence: Unlocking Hidden Text

The research team, including scientists from SLAC National Accelerator Laboratory and Sorbonne University, employed X-ray fluorescence technology to reveal the erased script. This method differentiates between the distinct chemical compositions of inks from different eras. The ink used by the monks for the top layer is rich in iron, whereas the underlying Greek text exhibits a strong calcium signal. By tuning an X-ray beam, researchers create elemental maps, effectively separating these layers to view the hidden text without physical obstruction.

The scanning process, which commenced with 11 manuscript pages provided by the Museum of the Bible, involves a synchrotron at SLAC. This particle accelerator propels electrons to near light speed, producing X-rays when directed by magnets. To protect the fragile parchment, each 10-millisecond X-ray pulse targets a spot the width of a human hair, maintaining a radiation dose well below safe limits. Sam Webb, a lead scientist at SLAC, contributed to building the instrumentation for these X-ray experiments.

Initial Discoveries and Progress

Initial scans have revealed words such as "Aquarius" and descriptions of "bright" stars within that constellation. Researcher Victor Gysembergh from Sorbonne University noted the ongoing revelation of ancient Greek text. The resolution provided by SLAC's X-ray fluorescence technology is significantly higher than that of multispectral imaging, which previously yielded only fragments.

The project involves advanced data processing techniques to statistically separate text from the front and back of pages, as X-rays penetrate both sides simultaneously, sometimes revealing up to six layers of ink. Keith Knox, an imaging scientist, noted this project contributes to a decades-long effort to recover historical information.

Profound Historical and Scientific Significance

Hipparchus, active between approximately 190 and 120 BCE, is recognized for his monumental contributions to astronomy. These include mapping stars, determining the shift of equinoxes, developing a magnitude scale for star brightness, and tracking planetary motion, all achieved without modern instruments. The recovered coordinates now offer unprecedented insight into ancient astronomical practices and their precision.

The findings are expected to address historical debates, particularly regarding whether the Roman astronomer Ptolemy plagiarized Hipparchus’s star catalog. By comparing the newly acquired data with Ptolemy’s preserved records, researchers anticipate demonstrating that Ptolemy combined Hipparchus’s data with other sources, indicating a process of scientific compilation rather than plagiarism.

The project aims to recover as many coordinates as possible to contribute to understanding the origins of science and the accuracy of ancient astronomical observations made without telescopes.

Logistics and The Path Forward

The 11 scanned folios were transported from the Museum of the Bible in humidity-controlled cases with a strict hand-carry policy. Elizabeth Hayslett, a conservator from the Museum of the Bible, prepared the pages, and lights in the scanning room are kept low to prevent ink fading. These pages are part of a larger 200-page codex, with other sections located globally, potentially requiring further coordination for a complete reconstruction.

The next phase of the project involves ancient Greek scholars translating the recovered coordinates and descriptions, aiming to reconstruct Hipparchus’s lost catalog. Sophia Vogelsang, a Chemistry Ph.D. student, expressed hope that demonstrating the utility of this scientific approach will encourage collaboration with more scholars possessing historically significant documents.