Jacques Cassini

News of the discovery of the Comet of 1729 had been passed to Jacques Cassini in Paris.

He is able to confirm the comet's position, though with extreme surprise at how little it had moved since the first observation nearly a month previously.

Cassini is able to continue observation until January 18, 1730, by which time the comet is located in Vulpecula.

This is an extraordinarily long period for observation of a comet, though it never rises above apparent magnitude 3-4.

The comet’s orbit, later computed by John Russell Hind, shows a perihelion distance (closest approach to the Sun) of 4.05054 AU which is just within the orbit of Jupiter.

However despite this it became visible, although faintly, to the naked eye, and indeed remains visible for six months in total.

This suggests that its absolute magnitude or intrinsic brightness is unusually high, possibly as high as -3.0.

It is therefore likely that the Comet of 1729 was an exceptionally large object, with a cometary nucleus of the order of one hundred kilometers in diameter.

The JPL small-body database only uses three observations, a two-body model, and an assumed epoch to compute the orbit of this parabolic comet.

There is significant debate in the scientific community, specifically in the French Academy of Sciences (Académie des sciences), as to whether the circumference of the Earth is greater around the Equator or around the poles.

French astronomer Jacques Cassini holds to the view that the polar circumference is greater.

Louis XV, the King of France, and the Academy send two expeditions to determine the answer: one is sent to Lapland, close to the North Pole, under Swedish physicist Anders Celsius and French mathematician Pierre Maupertuis.

The other mission is sent to Ecuador, at the Equator.

Previous accurate measurements had been taken in Paris by Cassini and others.

The equatorial mission is led by French astronomers Charles Marie de La Condamine, Pierre Bouguer, Louis Godin and Spanish geographers Jorge Juan and Antonio de Ulloa.

They are accompanied by several assistants, including the naturalist Joseph de Jussieu and Louis's cousin Jean Godin.

La Condamine will be joined in his journey down the Amazon by Ecuadoran geographer and topographer Pedro Maldonado. (Maldonado will later travel to Europe to continue his scientific work.)

The Ecuadoran expedition leaves France in May 1735.