Hipparchus’ catalog of stars finally discovered on a parchment?

Researchers believe they have found Hipparchus’ star catalog. The various indices seem to agree.

In 2012, while analyzing a Christian manuscript, a student discovered, behind the lettering of certain pages, hidden texts. A recent “autopsy” of the 146 pages of the work carried out using state-of-the-art multispectral imagery has made it possible to decipher some of its secrets: astronomical material in Greek, probably written in the 5th or 6th century. It is about myths about the origin of the stars of Eratosthenes and a poem from the third century BC, the Phenomena of Aratos de Soles. But there could be even more interestingthe catalog ofstars of Hipparchus.

Researchers believe they have found Hipparchus’ star catalog

On one page, a sort of “surviving” text stands out from the rest. The researchers published their findings in the Journal for the History of Astronomywith an explanatory paper on the site Science. They believe it may be part of Greek astronomer Hipparchus’ long-lost and sought-after star catalog. This document is considered the first known attempt to map the night sky.

At that time, it was quite common for scholars to reuse ancient scrolls. The manuscript in question is a palimpsest, a writing medium on which the older text has been scraped off by the scribe so that it can be reused. On one page, the experts spotted odd numbers, eventually identified as star coordinates. These numbers indicate the length and width in degrees of a single constellation, the Corona Borealis, as well as those of nearby stars. We can notably read: “The Corona Borealis, located in the northern hemisphere, extends in length from 9°¼ of the first degree of Scorpio to 10°¼8 in the same zodiacal sign. In width, it extends 6°¾ from 49° North Pole to 55°¾.”

The different indices seem to agree

Impossible to affirm the provenance of this writing with certainty, unfortunately, but we know that the Greek astronomer Hipparchus was working on a catalog of stars in the sky of the Western world at the same time. Hipparchus is one of the first known figures among specialists in astronomy. Some texts designate him as “the father of astronomy” or “the greatest astronomer of ancient Greece”. It is he who would have discovered the precession or the calculations of the gymnastics of the Sun and the Moon.

And as a coincidence, the only “official” handwritten trace left by Hipparchus is a commentary on the poem, the Phenomena of Aratos. In the latter, many coordinates correspond to those of the document that interests us today. Moreover, by going back in time, the experts have calculated that the coordinates of the stars revealed in this manuscript more or less correspond to the expected precession of our planet during the lifetime of Hipparchus.

And as if that were not enough, the star values ​​of the constellations mapped there also correspond to those of his commentary. These clues therefore suggest that Hipparchus is the origin of the coordinates cited in these documents. And the discovery of new text adds some weight to this idea. For Mathieu Ossendrijver, historian of astronomy at the Free University of Berlin, “the new fragment makes this much, much clearer. This catalog of stars that hovered in the literature as an almost hypothetical thing has become very concrete.”

This discovery would also settle the question of the relationship between Ptolemy and Hipparchus, the first would have stolen the work of the second. Hipparchus’ observations, correct to within a degree, seem more accurate than those of his successor, so they would not have been copied. And the systems are different, Ptolemy would have based himself on the ecliptic where Hipparque used the celestial equator.

According to the researchers, this manuscript could still have a lot to reveal, more coordinates of stars could be deciphered. To be continued !

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