DDA2001, April2001
Session 12. Planetary Dynamics
Wednesday, 1:00-2:30pm

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[12.01] Galileo's Observations of Neptune

E. M. Standish (JPL)

In 1979, Stillman Drake and Charles Kowal found that the astronomer Galileo actually observed the planet Neptune in the years 1612 and 1613. Galileo's observing notebooks still exist and are preserved in the National Central Library in Florence, Italy. In them, one can see the discovery of the four large moons of Jupiter, and one can follow the subsequent work of Galileo as he improved his telescopes, charted the nightly positions of the satellites, and refined his ability to predict their future configurations. One sees his observing innovations and improving accuracies which seem to reach a crescendo just at the time of his observations of Neptune.

Further scrutiny of Galileo's notebooks has revealed other intriguing observations. One is a probable fourth observation of Neptune which has a direct bearing upon present-day ephemerides. There are also observations of two other objects which, to this day, despite some effort, remain unidentified - possibly asteroids, comets, novae, or supernovae.

More than of just historical interest, Galileo's work still has important implications for present-day astronomy.

The research described in this talk was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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