The Farnese Atlas is a 2nd-century Roman marble copy of a Hellenistic sculpture of Atlas kneeling with a globe weighing heavily on his shoulders. It is the oldest extant statue of the Titan of Greek mythology, who is represented in earlier vase-painting, and more important, the oldest known representation of the celestial sphere. The sculpture is at the National Archaeological Museum (Museo Archeologico Nazionale) in Naples, Italy. It stands seven feet (2.1 meters) tall, and the globe is 65 cm in diameter.
Atlas labors under the weight because he had been sentenced by Zeus to hold up the sky. The globe shows a depiction of the night sky as seen from outside the outermost celestial sphere, with low reliefs depicting 41 (some sources say 42) of the 48 classical Greek constellations distinguished by Ptolemy, including; Aries the ram, Cygnus the swan and Hercules the hero. The Farnese Atlas is the oldest surviving pictorial record of Western constellations. It dates to Roman times, around AD 150, but has long been presumed to represent constellations mapped in earlier Greek work.
Dating the original 
In 2005, at a meeting of the American Astronomical Society in San Diego, California, Dr. Bradley E. Schaefer, a professor of physics at Louisiana State University, presented a widely reported analysis concluding that the text of Hipparchus' long lost star catalog may have been the inspiration for the representation of the constellations on the globe, thereby reviving and expanding an earlier proposal by Georg Thiele (1898). The constellations are fairly detailed and Schaefer regards them as scientifically accurate given the period of the globe's creation, implying that it was modeled after a scholarly work. His statistical analysis concludes that the positions of these constellations are consistent with where they would have appeared in the time of Hipparchus (129 BC) - leading to the conclusion that the statue is based on the star catalog.
However, because the globe contains no actual stars, and because the circles on the globe are drawn inexactly and ambiguously by a sculptor copying the Hellenistic model rather than by a modern astronomer, the dating of the globe is still uncertain and its source or sources remain controversial; Schaefer's conclusions have been strongly contested (e.g, Dennis Duke, Journal for the History of Astronomy, February 2006) most particularly on the ground that regardless of the globe's date the constellations on it show large disagreements with the only existing work by Hipparchus.
- Bradley E. Schaefer, "The epoch of the constellations on the Farnese Hercules and their origins in Hipparchus's lost catalogue"
- N.Y. Times article on Dr. Schaefer's presentation
- Space.com article on the Hipparchus' star catalogue found.
- National Archaeological Museum, Naples, Italy
- Critiques of Schaefer's hypothesis
- Critical review of Schaefer's arithmetic, quotations, statistics, photogrammetry, grasp of Hipparchus's data, and responsiveness
- Related critical review, containing detailed photographic images