DISCOVERY OF HIPPARCHUS’ LOST STAR CATALOG ON

THE FARNESE ATLAS

BRADLEY E. SCHAEFER(Louisiana State University)

HIPPARCHUS -Greatest Astronomer of Antiquity

• First Star Catalog (~1000 stars)• Discovered Precession• First Nova• First Model for Solar & Lunar

Motion• Best Planetary Observations to

Date

Rhodes: fl. 140-125 BC

Only surviving work is his Commentary

FARNESE ATLAS SHOWS:

• 41 Constellations

(no stars)• Equator, Tropics• Colures• Arctic, Antarctic

Circles

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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 BCAssyrian observer who was source for

Eudoxus and MUL.APIN

GET DATE FROM CONSTELLATION POSITIONS

Constellations positions shift slowly with the centuries (due to precession), so the depicted positions provide a ‘clock’

PRECESSION

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DATE OF FARNESE ATLAS CONSTELLATION DATA

• New photographs taken in Naples last JuneNew 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

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 Ptolemyhave old star catalogs

(and Ptolemy is too late)

DETAILED COMPARISON BETWEEN ATLAS AND ANCIENT SOURCES

• Phaenomena of Aratus & Eudoxus12 significant differences

e.g., solstice off by 35°!, Centaur not under Scorpion, Eridanus extends almost to Dog

• Commentaries of Hipparchus0 differences

• Catasterismi of Pseudo-Eratosthenes & Eratosthenes9 significant differences

e.g., Southern Crown is present, Hercules is kneeling, Pegasus has wings

• Almagest of Ptolemy11 significant differences

e.g., Equuleus and Bernices’ Hair missing, Eridanus extends almost to Dog, Archer has no cloak

CONNECTING THE FARNESE ATLAS TO HIPPARCHUS’ CATALOG

• 3.5° ACCURACY REQUIRES A STAR CATALOGOnly Hipparchus and Ptolemy have ancient star catalog

• FARNESE ATLAS POSITIONS FROM 125 ± 55 BCEliminates Ptolemy, Aratus, Eudoxus, the Assyrian, and any contemporaryOnly Hipparchus is consistent with date

• CONSTELLATION ICONS MATCH HIPPARCHUSEliminates Ptolemy, Aratus, Eudoxus, and EratosthenesOnly Hipparchus matches the Farnese Atlas

FARNESE ATLAS BASED ON THE LOST STAR CATALOG OF HIPPARCHUS

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

CONCLUSIONSTHE LOST STAR

CATALOG OF HIPPARCHUS IS DEPICTED ON THE FARNESE ATLAS