The discovery of Amalthea, one of Jupiter’s moons, on September 9, 1892, was made by the American astronomer Edward E. Barnard. Utilizing a state-of-the-art telescope at the time, Barnard meticulously tracked and observed celestial movements in amateur and professional astronomy. Unlike other astronomical discoveries that increasingly depended on photography, Barnard relied solely on direct visual observation through his telescope, marking Amalthea as the last moon to be found using purely observational methods. Amalthea is notable for its asymmetrical, irregular shape, measuring approximately 250 kilometers in diameter and characterized by a reddish hue, signaling that it may be composed of a significant amount of non-icy material, a unique feature among moons in the Jovian system. Barnard’s work not only added to the known celestial bodies orbiting Jupiter but also placed him among the leading figures in astronomy during his era.

The period in which Amalthea was discovered was crucial for astronomical advancements, as the late 19th century was marked by significant improvements in telescope technology. Barnard's discovery highlighted the potential of detailed observing techniques and set the stage for future explorations of the planet Jupiter and its moons. His persistence in observing celestial events opened doors for further investigations into the characteristics of asteroids and other irregular celestial bodies, paving the way for modern observational astronomy. The significance of Amalthea extends beyond its own composition; it symbolizes a transition in astronomical techniques, differentiating between purely visual observation and the emerging techniques that would dominate in the decades to follow.