The discovery of Titan, Saturn's largest moon, was made by the astronomer Christiaan Huygens in 1655. Using a telescope he had designed and constructed himself, Huygens aimed to explore the heavens and study celestial phenomena, including the rings of Saturn, which was already known to be a remarkable feature of the planet. As he turned his attention toward Saturn, Huygens made a significant observation: he detected a large moon orbiting the planet, which he later named Titan, derived from the Titans of Greek mythology.

Huygens detailed this moon’s discovery in his work, 'Systema Saturnium,' which provided not only descriptions of his observations but also speculative theories regarding its atmosphere and surface characteristics. At the time of its discovery, Titan was the only moon known to orbit Saturn, and it became an object of intrigue for scientists and astronomers alike due to its substantial size and unique features. Over the years, Titan has been subject to extensive study, revealing a thick atmosphere that is primarily composed of nitrogen, along with the existence of lakes and rivers of methane and ethane.

The discovery of Titan not only enriched the understanding of moons within our solar system but also raised important questions regarding the possibility of life and alien atmospheres beyond Earth. Huygens’ meticulous observations and descriptions set a precedent for future investigations into celestial bodies and encouraged further exploration of the outer solar system, paving the way for later missions such as the Cassini-Huygens mission, which provided vast amounts of data about Saturn and Titan in particular.