DISCOVERY OF HIPPARCHUS’ LOST STAR CATALOG ON THE FARNESE ATLAS BRADLEY E. SCHAEFER (Louisiana State University)

1. DISCOVERY OF HIPPARCHUS’ LOST STAR CATALOG ON THE FARNESE ATLASBRADLEY E. SCHAEFER(Louisiana State University)

2. HIPPARCHUS -Greatest Astronomer of Antiquity Rhodes: fl. 140-125 BC Only surviving work is his Commentary • First Star Catalog (~1000 stars) • Discovered Precession • First Nova • First Model for Solar & Lunar Motion • Best Planetary Observations to Date

3. FARNESE ATLAS SHOWS: • 41 Constellations (no stars) • Equator, Tropics • Colures • Arctic, Antarctic Circles

4. POSSIBLE DATES FOR OBSERVATIONS USED TO PLACE THE CONSTELLATIONS • c. 150 AD Contemporary with Roman sculptor • c. 128 AD From Ptolemy’s Almagest • c. 275 BC From Aratus’ Phaenomena • c. 366 BC From Eudoxus’ Phaenomena • 1130±80 BC Assyrian observer who was source for Eudoxus and MUL.APIN

5. GET DATE FROM CONSTELLATION POSITIONS Constellations positions shift slowly with the centuries (due to precession), so the depicted positions provide a ‘clock’

6. PRECESSION

7. DATE OF FARNESE ATLAS CONSTELLATION DATA • New photographs taken in Naples last June New photos required as camera-globe distance must be known for photogrammetry • 70 constellation positions measured to 1.5° accuracy • Chi-square fit to find the best date 125 BC(±55 years) REJECTS Ptolemy, Aratus, Eudoxus, and the AssyrianMATCHES Hipparchus

8. DATE OF FARNESE ATLAS CONSTELLATION DATA • Accuracy of original data is <2° • Ancient star catalogs have accuracy <1° • Ancient verbal descriptions have accuracy >4°-8° Original data must be from a star catalog Only Hipparchus and Ptolemy have old star catalogs (and Ptolemy is too late)

9. DETAILED COMPARISON BETWEEN ATLAS AND ANCIENT SOURCES • Phaenomena of Aratus & Eudoxus 12 significant differences e.g., solstice off by 35°!, Centaur not under Scorpion, Eridanus extends almost to Dog • Commentaries of Hipparchus 0 differences • Catasterismi of Pseudo-Eratosthenes & Eratosthenes 9 significant differences e.g., Southern Crown is present, Hercules is kneeling, Pegasus has wings • Almagest of Ptolemy 11 significant differences e.g., Equuleus and Bernices’ Hair missing, Eridanus extends almost to Dog, Archer has no cloak

10. CONNECTING THE FARNESE ATLAS TO HIPPARCHUS’ CATALOG • 3.5° ACCURACY REQUIRES A STAR CATALOG Only Hipparchus and Ptolemy have ancient star catalog • FARNESE ATLAS POSITIONS FROM 125 ± 55 BC Eliminates Ptolemy, Aratus, Eudoxus, the Assyrian, and any contemporary Only Hipparchus is consistent with date • CONSTELLATION ICONS MATCH HIPPARCHUS Eliminates Ptolemy, Aratus, Eudoxus, and Eratosthenes Only Hipparchus matches the Farnese Atlas FARNESE ATLAS BASED ON THE LOST STAR CATALOG OF HIPPARCHUS

11. APPLICATIONS • WHAT COORDINATE SYSTEM DID HIPPARCHUS USE? None? Equatorial? Ecliptic? Mixed? EQUATOR, COLURES, TROPICS EQUATORIAL COORDINATES • HOW MUCH OF HIPPARCHUS’ CATALOG IS IN THE ALMAGEST? None? Small fraction? Large fraction? All? In past, we have only had partial positions for some stars (from the Commentary) are known, and these have an unknown relation to the star catalog NOW, WE HAVE HIPPARCHUS’ FULL CATALOG  FUTURE WORKERS WILL TEST FARNESE ATLAS vs. ALMAGEST

12. CONCLUSIONS THE LOST STAR CATALOG OF HIPPARCHUS IS DEPICTED ON THE FARNESE ATLAS