Stars in History of Science

Very exciting news for the field of history of science came out about a month ago: the first known star catalogue ever written was finally discovered in an old parchment originally kept at St. Catherine’s Monastery, in Sinai, Egypt. The parchment consists of 146 leaves of Syrian texts containing –behind them– a palimpsest, which is an older work that has been scraped out.

Scholars and scientists are now able to access palimpsests such as these using multispectral imagery. What they found in the case of this parchment was a set of coordinates for the position of stars belonging to the Corona Borealis constellation. As stars are seen to be shifting slowly to the west in a movement known as precession, the values are different from the modern ones and –more surprisingly still– they even differ from those given by Ptolemy in the oldest catalogue extant. So, the question that remained was: whose measurements were they? And when were they taken? By accounting for the movement of precession, it was possible for scholars to determine that the coordinates were taken around the second century B.C. and would most likely belong to the ancient astronomer Hipparchus, whose catalogue is known only because it was mentioned by later authors.

Stars are a fascinating topic for us members of the RUTTER project, for they played a crucial role in navigation. Latitude measurements at night were based on the determination of the position of the Poles through visible stars –Poles which were still relatively distant from Polaris and even more so from the Southern Cross, in the northern and southern hemispheres respectively. Longitude values, although not so frequent, could also be taken through the stars. The lunar distance method, for instance, could be used by measuring the angular distance between the moon and a particular fixed star in two different places. Sailors in the Indian Ocean had also developed a stellar compass rose in which the rising and setting position of 16 stars would mark the cardinal points and, thus, serve as indicators of direction.

It was with great excitement that we read about such an amazing historical finding as a part of Hipparchus star catalog, and we wonder at the potential impact that this discovery will have. [Inês Bénard]