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January 30, 2026<\/p>\n
3 min read<\/p>\n
Add Us On Google<\/span>Add SciAm<\/span><\/span><\/p>\n Lost ancient Greek star catalog decoded by particle accelerator<\/p>\n Synchrotron radiation has revealed a star map made by the ancient astronomer Hipparchus that was thought to be lost to time<\/p>\n By K. R. Callaway edited by Clara Moskowitz<\/span><\/p>\n X-ray fluorescence imaging is illuminating Hipparchus’ lost star catalog, allowing researchers to learn more about ancient astronomy.<\/p>\n Jacqueline Ramseyer Orrell\/SLAC National Accelerator Laboratory<\/p>\n Before telescopes, ancient Greek astronomers relied on naked-eye observations of the night sky to understand the universe around them. The meticulous star catalog belonging to one of the best of these observers, Hipparchus, was long thought to be lost to time, but a hidden copy survived centuries. Erased and buried beneath layers of other text in a medieval codex, the catalog was nearly unreadable\u2014until now.<\/p>\n 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 earliest astronomers\u2019 methods were and how Hipparchus\u2019s work influenced later scientists.<\/p>\n \u201cSince this star catalog is so important for understanding the birth of science, it made us want to pull out all the stops,\u201d says Victor Gysembergh, a researcher at the French National Center for Scientific Research (CNRS), who led the experiment. \u201cWhat we\u2019ve been seeing is amazing in comparison to previous imaging.\u201d<\/p>\n If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n The researchers\u2019 journey with the document began in 2021, when they uncovered constellation names and measurements attributable to Hipparchus hidden under layers of other text in the Codex Climaci Rescriptus, a palimpsest with portions dating back from the fifth century C.E. to the ninth or 10th century.<\/p>\n The term \u201cpalimpsest\u201d comes from ancient Greek words meaning \u201cscraped again\u201d and denotes a manuscript that has had its words erased and written over. Such erasure was a common practice throughout history to repurpose expensive parchments, but it poses a unique challenge for scholars hoping to uncover lost texts. For centuries, scientists have tried different lighting and chemicals to bring back erased texts. Modern imaging techniques using particle accelerators offer the best view yet.<\/p>\n The synchrotron that was employed in the new experiment operates at the SLAC National Accelerator Laboratory in Menlo Park, Calif. It works by accelerating charged particles to nearly the speed of light and circulating them around a curving track. As the particles constantly change direction, they emit exceedingly bright beams of x-ray light. This light can penetrate deep into materials and create a thorough x-ray image of an object.<\/p>\n Researchers are recovering the ancient manuscript\u2019s lost text using modern technology\u2014a synchrotron at the SLAC National Accelerator Laboratory.<\/p>\n Jacqueline Ramseyer Orrell\/SLAC National Accelerator Laboratory<\/p>\n This month scientists shined the beams on the Codex Climaci Rescriptus. The light reacted differently to different inks used through the centuries\u2014in some cases, it scattered, and in others, it diffracted or was absorbed. Newer inks on the palimpsest\u2019s top layers contained more iron, whereas those used to transcribe Hipparchus\u2019s catalog a few hundreds of years earlier left a calcium-rich residue that researchers zeroed in on with the x-ray imagery.<\/p>\n \u201cLuckily, these documents have been very well preserved, and we\u2019ve seen beautiful images and beautiful text,\u201d says Samuel Webb, lead staff scientist at the SLAC National Accelerator Laboratory\u2019s Stanford Synchrotron Radiation Lightsource.<\/p>\n Some analysis will have to wait until the new images can be processed, but the researchers are already able to decode text from many of the raw data. \u201cIt\u2019s one of the rare examples in research where you know very quickly that you have gotten good results,\u201d says Uwe Bergmann, a physics professor at the University of Wisconsin\u2013Madison, who is overseeing the experiment\u2019s x-ray scanning.<\/p>\n When their analysis is completed, the researchers expect the Codex Climaci Rescriptus to be the most complete repository yet of Hipparchus\u2019s observations. Still, it is not our only view into the astronomer\u2019s work.<\/p>\n While Hipparchus\u2019s star catalog was lost, his commentary associated with the work was passed down through the ages, explains Bradley Schaefer, a historian of astronomy at Louisiana State University, who was not involved in the experiment. That commentary, alongside works from other authors who mention Hipparchus\u2019s data and a Hipparchic star map accurately rendered on a statue called the Farnese Atlas, have given scholars of classical astronomy a good idea of Hipparchus\u2019s astronomical information.<\/p>\n \u201cThe great promise of this SLAC idea is, from another page of that palimpsest, you might be able to recover substantial amounts of [previously unknown] text,\u201d Schaefer says. He adds that the newly uncovered pages might lead to valuable information that will tell us more about Hipparchus and his discoveries or that will put to rest age-old questions about whether later renowned astronomers\u2014such as Ptolemy\u2014were making original observations or, in part, compiling the work of those who came before them.<\/p>\n With image processing and analysis by more scholars on the horizon, researchers involved in the synchrotron experiment hope their work will do more than illuminate the ancient science hidden in the Codex Climaci Rescriptus. \u201cThe manuscript is exceptionally interesting,\u201d Gysembergh says. \u201cBut it\u2019s also a chance to jump-start more studies like this on more manuscripts.\u201d<\/p>\n If you enjoyed this article, I\u2019d like to ask for your support. 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I hope you\u2019ll support us in that mission.<\/p>\n","protected":false},"excerpt":{"rendered":" January 30, 2026 3 min read Add Us On GoogleAdd SciAm Lost ancient Greek star catalog decoded by particle accelerator Synchrotron radiation has revealed a star map made by the ancient astronomer Hipparchus that was thought to be lost to time By K. R. 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