Major Moons - Random Trivia Answers

• A1) Jupiter. Since 2004, the largest planet has had 63 known moons, fourteen of which remain unnamed. Saturn has been closing the gap but currently stands at 61, eight of which remain unnamed.
• A2) The moon. Our moon has a diameter 27.2% of the Earth's. Charon has a diameter 52.3% of Pluto's, one of the main reasons the former ninth planet got demoted.
• A3) Triton. The largest irregularly shaped (non-spherical) moon has a diameter 5.5% of Neptune's, edging out Titan (4.3% of Saturn's) and Ganymede (3.7% of Jupiter's).
• A4) Titan. In 1655, Dutch astronomer Christiaan Huygens used a refracting telescope that he invented to spot Saturn's largest satellite.
• A5) Iapetus. From 1671 to 1684, Italian-born, French astronomer Giovanni Domenico Cassini discovered the four moons of Saturn he called Sidera Lodoicea (the Louisian Stars, in honor of his benefactor France's King Louis XIV). The other three moons, later named Rhea, Tethys, and Dione, would be the last new moons found for over a century.
• A6) Adrastea. Pictures taken from Voyager I on July 8, 1979 revealed Jupiter's inner moon, the first moon alphabetically. Saturn's Janus had already been noted from Earth as far back as 1966, but Voyager I confirmed its existence in 1980.
• A7) Mars. Despite its relative nearness, Mars was officially moonless until Deimos and Phobos were spotted 1877, after Jupiter (Io, Europa, Ganymede, and Callisto in 1610), Saturn (Titan in 1655), Uranus (Titania and Oberon in 1787), and even Neptune (Triton in 1846).
• A8) Neso. Neso takes a whopping 9,374 days (25.7 years) to orbit Neptune. The next three slowest (Psamathe, Laomedeia, and Sao) also belong to the eighth planet. At the other extreme, Naiad and Metis only need seven hours to circle Neptune and Jupiter respectively.
• A9) Phobos. With a semi-major axis (the larger "radius" of the ellipse) of only 5,828 miles, Phobos actually revolves around Mars faster than Mars rotates. Its twin Deimos is the second closest at 14,577 miles.
• A10) Ganymede. The largest satellite in both volume and weight orbits Jupiter, edging Saturn's Titan in both categories.
• A11) Io. Slightly larger than the moon and less slightly heavier, Jupiter's Io is the only satellite on which you weigh more than you would on the moon. Ganymede and Titan both have lower enough densities to offset their larger sizes.
• A12) Y. Ymir, named for the giant whose body Odin used to create the world in Norse mythology, was discovered orbiting Saturn in 2000. The letters Q and V also begin the names of no moons.