The world’s oldest map of the night sky was amazingly accurate

Newly discovered fragments of 2,200-year-old star coordinates—once thought lost—reveal the incredible skill of the ancient astronomer Hipparchus.

Some 2,200 years ago, the Greek astronomer Hipparchus helped a new way of understanding the motions of the stars that persists to this day. By imagining Earth at the center of a celestial sphere, he used a coordinate system similar to latitude and longitude, which had recently been devised, to measure the precise positions of the stars.

“He was arguably the greatest ancient astronomer. At least the greatest known to us by name,” says Victor Gysembergh, a science historian at the French National Center for Scientific Research.

Many ancient Greek scientists believed that Earth was literally at the center of the universe, and the stars and other celestial bodies rotated around it, although a model with Earth orbiting the sun was in the 3rd century B.C. Although this geocentric model is incorrect, the concept, which Hipparchus used to create the first known star catalog, is still used by scientists to map objects in the sky.

Hipparchus’s star catalog is the oldest known attempt to document the positions of as many objects in the night sky as possible, and it was the first time that two coordinates were used to pinpoint each object’s location. But that original catalog is lost to time, and we know of it only thanks to the writings of later scientists such as Ptolemy, who created his own star catalog around 150 A.D. and attributed an earlier one to Hipparchus. Until now, the oldest evidence for stellar coordinates from Hipparchus was an 8th-century A.D. Latin translation of a poem about the constellations that includes the coordinates as a kind of annotation.

Gysembergh and his recently revealed even older evidence of star coordinates from Hipparchus in a 5th- or 6th-century A.D. Greek version of the same poem, Phenomena, originally written by the Greek poet Aratus in the 3rd century B.C. The poem, along with the accompanying star coordinates, had been erased from a reused medieval parchment and was recovered only through multispectral imaging, which uses different wavelengths of light to highlight the removed text.

The coordinates for the four stars to the farthest north, south, east, and west of the constellation Corona Borealis are included, though one of them could not be recovered from the manuscript. They were found to be accurate to within one degree of modern values—a remarkable achievement for someone working about 1,700 years before the invention of the telescope.

(Fonte: National Geographic - adaptado.)