Jupiter’s moon Amalthea was discovered in 1892. American astronomer Edward Emerson Barnard found it on September 9 of that year while using the 36-inch refractor telescope at Lick Observatory in California.
Amalthea was the first new moon of Jupiter discovered after Galileo Galilei identified the four large Galilean moons in 1610. It was also the last planetary satellite discovered by direct visual observation; later satellite discoveries relied on photographic or digital imaging.
Amalthea is a small, irregularly shaped moon with a notably reddish surface. It orbits Jupiter inside the orbits of the Galilean moons and is the planet’s third-closest known natural satellite. Its elongated shape results from its low gravity and its rapid, tidally locked orbit around Jupiter.
The year 1904 is sometimes confused with later discoveries of Jovian satellites, while 1610 belongs to Galileo’s discovery of Io, Europa, Ganymede, and Callisto. Amalthea’s discovery date is firmly established as 1892.