Parts of the Hipparchus catalogue, the oldest known map of the sky

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Hipparchus. Photo: author unknown/Wikimedia Commons, public domain


  • Parts of Hipparchus’ famous star catalog, the oldest known map of the sky, have been discovered hidden beneath medieval Christian texts from Egypt.
  • The manuscript was a palimpsest – a scroll that was scraped from an older text for reuse. The oldest text was also believed to be an earlier Christian scripture.
  • The deciphered passage describes the length and width in degrees of the constellation Corona Borealis and gives the coordinates of the stars at its north, south, east and west ends.

New Delhi: Parts of Hipparchus’ famous star catalogue, the oldest known map of the sky, have been discovered hidden beneath medieval Christian texts from Egypt – a development described as “rare” and “remarkable”.

The findings were presented in an article published in the astronomy history journal. Nature News said the catalog was found hidden in a palimpsest manuscript – a scroll that was scraped from an older text for reuse. “The manuscript originates from the Greek Orthodox Monastery of St. Catherine in the Sinai Peninsula, Egypt, but most of its 146 leaves, or folios, now belong to the Museum of the Bible in Washington DC,” its report states.

The rewritten manuscript, called Codex Climaci Rescriptus, contains a collection of Syriac texts written in the 10th or 11th century AD. The older script was also thought to contain Christian writings, but a few years ago analysis showed that nine folios revealed astronomical material that was probably transcribed in the 5th or 6th century AD.

The latest discovery is that a one-page surviving passage was written by Hipparchus, describing the length and width in degrees of the constellation Corona Borealis and giving the coordinates of the stars at its northern, southern, eastern and western extremes.

Hipparchus published the first comprehensive star catalog during the second century BC, charting the positions of 850 stars using a simple sight tube (diopter) astrolabe and a mechanism called the armillary sphere. It has been used for centuries but was lost long ago.

Describing the importance of Hipparchus’ catalog, Nature News said his efforts marked a “pivotal moment in the birth of science, when astronomers moved from simply describing the patterns they saw in the sky to measuring and predicting”.

Saint Catherine’s Monastery, Sinai, Egypt, where the manuscript is from. Photo: Marc Ryckaert/Wikimedia Commons, CC BY 3.0

The new discovery

It was a student of Bible scholar Peter Williams at Cambridge University who made the initial discovery that a few pages of the Manuscript previously contained astronomical material. Willaims was ‘reviewing footage during a coronavirus lockdown’ when he noticed ‘something much more unusual’, according to Nature.

When this one-page passage was deciphered by historian Victor Gysembergh of CNRS in Paris and his colleague Emmanuel Zingg of Sorbonne University in Paris, they discovered that it described the constellation Corona Borealis, or the northern crown, and the stars around it.

In the article, the scholars have provided a simplified transcription and translation of the relevant sections which they believe were written by Hipparchus. It said:

“The corona borealis, located in the northern hemisphere, extends from 9°¼ of the first degree of Scorpio to 10°¼ in the same zodiacal sign (ie in Scorpio). In width, it extends 6°¾ from 49° from the North Pole to 55°¾.

Inside, the star (β CrB) to the west next to the bright (α CrB) leads (i.e. is the first to rise), being at Scorpius 0.5°. The fourth star (ι CrB) east of bright (α CrB) is the last (i.e. to rise) [. . .] 49° from the North Pole. The southernmost (δ CrB) is the third from the bright (α CrB) towards the East, which is 55°¾ from the North Pole.

According Nature Newsthe evidence points to Hipparchus as the source due to the idiosyncratic way in which some of the data was expressed, and which experts were able to date based on the “accuracy of the ancient astronomer’s measurements”.

The researchers were also able to use precession – a phenomenon in which the Earth slowly wobbles on its axis about a degree every 72 years, thereby slowly shifting the position of “fixed” stars in the sky – to check when the ancient astronomer must have made his observations. They found that the coordinates correspond roughly to 129 BC, when Hipparchus was working, Nature News said. It turns out that it was Hipparchus who discovered the precession of the Earth.

In the abstract, the authors of the paper write: “This new evidence is the most reliable to date and allows major advances in the reconstruction of Hipparchus’ star catalogue. In particular, it confirms that the star catalog was originally composed in equatorial coordinates.

They added that the available digital evidence is consistent with an accuracy within 1° of the actual stellar coordinates, which would make Hipparchus’ catalog much more accurate than that of his successor, Claudius Ptolemy – which is the only catalog of stars that has survived since antiquity. after being compiled in Alexandria, Egypt in the second century CE.

According Natureresearchers believe that Hipparchus’ original list would have included observations of nearly every star visible in the sky.

James Evans, an astronomy historian at the University of Puget Sound in Tacoma, Washington, said Nature that the discovery “enriches our picture” of Hipparchus. “It gives us a fascinating insight into what he actually did” and the “mathematization of nature.”

The report adds that Hipparchus merged the knowledge of the Babylonians to make precise observations and mathematical methods to model and predict the timing of events such as lunar eclipses with the Greek geometric approach, marking the beginning of modern astronomy. .

Are other discoveries waiting?

According Nature, the researchers hope that as imaging techniques improve, more palimpsests will be discovered and deciphered. “Several parts of the Codex Climaci Rescriptus have not yet been deciphered. It is also possible that additional pages of the Star Catalog survive in the St. Catherine’s Library, which contains over 160 palimpsests. Efforts to read them have already revealed previously unknown Greek medical texts, including drug recipes, surgical instructions, and a guide to medicinal plants,” the report states.

Multispectral palimpsest imagery “opens a rich new vein of ancient texts” in archives around the world, Nature said. “In Europe alone, there are literally thousands of palimpsests in major libraries,” says Gysembergh. “This is just one very exciting case of a research possibility that can be applied to thousands of manuscripts with amazing discoveries every time.”

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