Short answers, pulled from the story.
Astronomer Edward Emerson Barnard discovered Amalthea on the 9th of September 1892, using a 36 inch refractor telescope at Lick Observatory. It was the last moon of Jupiter ever found by direct visual observation, since every satellite discovered afterward turned up on a photograph or a digital image.
Amalthea is named for the nymph who nursed the infant Zeus, the Greek equivalent of Jupiter, with goat's milk. Camille Flammarion first suggested the name, though the International Astronomical Union did not formally adopt it until 1976, and the moon was known simply as Jupiter V before that.
Amalthea has a density as low as 0.86 grams per cubic centimeter, suggesting it is either a relatively icy body, a very porous rubble pile, or something in between. Infrared spectra from the Subaru telescope detected hydrous minerals, suggesting the moon formed farther from Jupiter or was captured from elsewhere in the Solar System.
Amalthea's largest crater, Pan, measures 100 kilometers across and is at least 8 kilometers deep. Its second crater, Gaea, measures 80 kilometers across and is likely twice as deep as Pan.
From Amalthea's surface, Jupiter would appear roughly 46 degrees across, about 85 times wider than a full moon looks from Earth. Because Amalthea is tidally locked, Jupiter would not appear to move across its sky, and the Sun would vanish behind Jupiter's bulk for about an hour and a half each orbit.
NASA's Juno probe, which reached Jupiter in 2016, is scheduled to make a close flyby of Amalthea on the 25th of April 2027. Earlier close encounters include imaging flybys by Voyager 1 and Voyager 2 in 1979 and a targeted Galileo flyby on the 5th of November 2002.