Lost ancient Greek star catalog decoded by particle accelerator
Synchrotron radiation has revealed a star map made by the ancient astronomer Hipparchus that is believed to have been lost to time.
X-ray fluorescence imaging is illuminating the lost star catalog of Hipparchus, allowing researchers to learn more about ancient astronomy.
Jacqueline Ramseyer Orrell/SLAC National Accelerator Laboratory
Before telescopes, ancient Greek astronomers relied on naked eye observations of the night sky to understand the universe around them. The astral star catalog of one of these best observers, Hipparchus, was long thought to be lost to time, but a hidden copy survived for centuries. Erased and hidden under layers of other text in medieval codexes, the catalog was almost unreadable until now.
Researchers say they have finally been able to decode some of the lost text using a type of particle accelerator called a synchrotron. They hope their analysis will shed light on what the methods of early astronomers were and how Hipparchus’s work influenced later scientists.
“Since this star catalog is so important for understanding the birth of science, it inspired us to pull out all the stops,” says Victor Gisembourg, a researcher at the French National Center for Scientific Research (CNRS) who led the experiment. “What we’re seeing is amazing compared to previous imaging.”
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The researchers’ journey with the document began in 2021, when they unveiled Names and measurements of constellations may be attributed to Hipparchus, hidden beneath layers of other text in Codex Climasi Rescriptus, A palimpsest containing fragments dating from the fifth century AD to the ninth or 10th century.
The word “palimpsest” comes from the ancient Greek words meaning “scraped again” and refers to a manuscript whose words have been erased and written over. This type of erasure was a common practice throughout history to reclaim expensive parchments, but it poses a unique challenge to scholars hoping to uncover lost texts. Over the centuries, scientists have tried various lighting systems and chemicals to recover erased texts. Modern imaging techniques using particle accelerators provide the best views to date.
The synchrotron that was employed in the new experiment operates at the SLAC National Accelerator Laboratory in Menlo Park, California. It works by accelerating charged particles almost to the speed of light and propel them around a curved track. As the particles constantly change direction, they emit extremely bright beams of X-ray light. This light can penetrate deep into the material and create a complete X-ray image of an object.
Researchers are recovering the lost text of an ancient manuscript using modern technology – a synchrotron at the SLAC National Accelerator Laboratory.
Jacqueline Ramseyer Orrell/SLAC National Accelerator Laboratory
This month scientists shined the rays Codex Climasi Rescriptus. Light reacts differently to the different inks used over the centuries – in some cases, it scatters, and in others, it is diffracted or absorbed. The new ink on the palimpsest’s upper layers contained more iron, while the ink used to write Hipparchus’ list a few hundreds of years earlier left a calcium-rich residue that researchers zeroed in on with X-ray imagery.
“Fortunately, these documents have been very well preserved, and we’ve seen beautiful images and beautiful text,” says Samuel Webb, chief staff scientist at SLAC National Accelerator Laboratory’s Stanford Synchrotron Radiation Lightsource.
Some analyzes will have to wait until the new images have been processed, but researchers have already been able to decode text from much of the raw data. “This is one of the rare examples in research where you find out very quickly that you’ve got a good result,” says Uwe Bergmann, a physics professor at the University of Wisconsin–Madison, who is overseeing the X-ray scanning of the experiment.
When their analysis is complete, the researchers hope Codex Climasi Rescriptus Being the most complete repository of Hipparchus’s observations ever made. Yet, this is not our only view of the astronomer’s work.
While Hipparchus’s star catalog was lost, his observations of the work survived for centuries, explains Bradley Schaefer, a historian of astronomy at Louisiana State University who was not involved in the experiment. That commentary, along with the works of other authors who mention Hipparchus’ data and the Hipparchus star map accurately presented on a sculpture called the Farnese Atlas, have given scholars of classical astronomy a good idea of Hipparchus’s astronomical knowledge.
“The big promise of this SLAC idea is that from another page of that palimpsest, you might be able to recover a substantial amount of (previously unknown) text,” says Schaefer. He adds that the newly uncovered pages may yield valuable information that will tell us more about Hipparchus and his discoveries or that will put to rest age-old questions about whether later famous astronomers—such as Ptolemy—were making original observations or, in part, compiling the work of those who came before them.
With image processing and analysis by more scholars on the horizon, researchers involved in the synchrotron experiment hope their work will do more than uncover the ancient science hidden within it. Codex Climasi Rescriptus. “The manuscript is exceptionally interesting,” says Giesemberg. “But it’s also a chance to launch more studies like this on more manuscripts.”
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