Themisto
Astronomers catch fleeting glimpses of a new natural satellite of Jupiter, Themisto, though the initial estimates of its orbit are “off” enough that Themisto becomes “lost” and isn’t observed again until 2000. With a diameter of roughly five miles, Themisto marks the dividing line between the larger inner moons of Jupiter and the widely-scattered menagerie of asteroid-like outer moons orbiting the planet. Astronomers Elizabeth Roemer and Charles Kowal (who discovered another new Jovian moon in 1974) share credit for discovering the moon. Themisto is the last Jovian satellite to be discovered by ground-based telescope in the 20th century.