Newton's Principia is published

Huygens's observational work linked improvements in telescopes with discoveries beyond Earth.

Cassini detected a moon later called Iapetus while observing Saturn.

Iapetus joined Titan among the known satellites of Saturn.

Cassini's later observations found the moon much easier to see on one side of Saturn than the other.

The discovery illustrates the expanding reach of systematic telescope observation.

The new work used the same gravitational principle to explain motion on Earth and in the heavens.

Newton presented mathematical arguments for orbital motion and other celestial phenomena.

Publication supplied tools for calculating motions of planets and comets, though later work refined them.

NASA's UTC catalog dates the transit to 6 June; some observers described it as 5 June in their local time.

Teams at widely separated sites recorded the transit to help estimate the Earth–Sun distance.