Astronomers Name Five of Jupiter’s New Moons

A contest earlier this year helped determine the names of the new moons—all named after lovers or offspring of the god Jupiter, aka Zeus

Jupiter Moons
Roberto Molar-Candanosa, courtesy of Carnegie Institution for Science

In 2018, astronomers at the Carnegie Institution for Science announced that they had discovered 12 new moons zipping around the outer reaches of the planet Jupiter, bringing the number of satellites orbiting the solar system’s largest planet up to a whopping 79. Now, five of those new moons have received official names proposed by the public during a contest earlier this year.

There are fairly strict guidelines for naming moons in Jupiter’s celestial family, also called the Jovian system. (So Moony McMoonface and Endor, sadly, did not make the cut.) Jupiter is, of course, named for the ancient Roman’s chief god, or Greek mythology’s equivalent to Zeus.

“There are many rules when it comes to how we name moons,” Scott Sheppard of the Carnegie Institution, who led that team that found the moons, says in a press release. “Most notably, Jovian naming conventions require its many moons to be named after characters from Greek and Roman mythology who were either descendants or consorts of Zeus, or Jupiter.”

According to International Astronomical Union, Jovian moons that move in the same direction as the planet’s rotation should end in the letter “a.” Those that move in a retrograde orbit, or the opposite direction of the spin, should end in an “e.” (There are exceptions.)

With those rules as a guide, as well as a 16 letter limit, the team solicited names in a contest running from March 1 to April 15 with people submitting their suggestions to @JupiterLunacy. Of course there were lots of entries that flouted the rules, suggesting the names of SciFi characters, famous scientists and family pets. There were plenty of Greek and Roman characters to pick from as well.

S/2017 J4, for instance, is now named Pandia, after the Greek goddess of the full moon. That name was submitted by several people, but the Institution particularly liked the entry from the Lanivet School in Cornwall, whose astronomy club tweeted a picture of the children holding up letters spelling out Pandia next to their panda mascot. The village, it turns out, used to supply bamboo to the London Zoo.

S/2018 J1 is now named Ersa, the Greek goddess of the dew, who is also Pandia’s sister and the daughter of Zeus by the goddess of the moon Selene. Several people also suggested that name, though the entry from four-year-old moon expert Walter, who sang a song about Jupiter’s moons, put Ersa over the top.

S/2003 J5 is now Eirene, named for the Greek goddess of peace, and S/2003 J15 has been dubbed Philophrosyne after the spirit of welcome and kindness. S/2003 J3 is now Eupheme named for the spirit of praise and good omen.

“I was blown away by the enthusiastic response for this contest,” Sheppard says in the release. “I hope the thought of these moons let everyone ponder the wonder and amazement that is our universe.”

Another moon, Valetudo, is named for the Roman goddess of health and hygiene, which is kind of ironic since it’s a pretty self-destructive moon. The rock is only about two-thirds of a mile in diameter and has a prograde orbit. That isn’t unusual except that it’s surrounded by objects with retrograde orbits, meaning every once in awhile it plays chicken with its neighbors. Researchers expect that sometime in the next billion years Valetudo will suffer a head-on collision detectable on Earth.

According to the Carnegie Institution, 64 out of Jupiter’s 79 moons are now named for Zeus’s lovers and descendants. Researchers expect to find even more moons around the gas giant named for a mythical god.

Which begs the question: are there enough names left to give Greco-Roman monikers to the remaining moons and those discovered in the future? Well, Zeus really got around, so even an incomplete list has more than enough divine, semi-divine and mortal lovers and their children to keep Moony McMoonface off the table for a long time.

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