Using a telescope of his own design and manufacture, Huygens discovers Titan, the largest moon of Saturn. This discovery significantly expands the known solar system.

Huygens correctly interprets the observations of Saturn's rings, determining them to be a thin, flat ring system not attached to the planet. He publishes his findings in 'De Saturni Luna Observatio Nova' ('New Observation Concerning Saturn's Moon').

Huygens publishes 'Systema Saturnium', detailing his observations of Saturn and its rings. The work solidifies his reputation as a leading astronomer and provides a comprehensive account of the Saturnian system as it was understood at the time.