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Telescopes. Historical artwork of a range of telescopes and four of the planets that they were used to study. Telescopes were developed in the 17th century, and were used to make many new discoveries. Galileo Galilei discovered four large moons orbiting Jupiter (1609), while Christian Huygens was the first to suggest that Saturn had rings (1655). The planets Uranus and Neptune were discovered using telescopes. Uranus was identified as a planet in 1781 by William Herschel. Neptune was identified as a planet independently in 1846 by Urbain Le Verrier, John Couch Adams, and Johann Gottfried Galle. (KEYSTONE/SCIENCE PHOTO LIBRARY/MEHAU KULYK/SCIENCE PHOTO LIBRARY)