Amateur astronomer Kai Ly has discovered a “new” moon orbiting Jupiter. Jupiter currently has 53 named moons, with 26 more moons orbiting Jupiter discovered so far awaiting official names. The new discovery raises that number to 27, bringing the total number of Jovian moons to 80.

Amateur Astronomers

Kai Ly previously recovered four “lost” moons of Jupiter. Now Ly has “located a previously unknown moon orbiting the biggest planet in our solar system” by examining old photos and star charts. Astronomy is one of the few sciences where determined amateurs can make major discoveries, like Maria Mitchell (1818-1889) discovering Miss Mitchell’s Comet in 1847 (aka C/1847 T1) or Alan Hale and Thomas Bopp discovering the Hale-Bopp Comet in 1995 or musician Willhelm Herschel (1738-1822) discovering the planet Uranus in 1781.

“I’m proud to say that this is the first planetary moon discovered by an amateur astronomer!” [Kai Ly] posted June 30 in a message at the Minor Planet Mailing List (MPML), an online community of the world’s leading amateur astronomers.

Science fiction authors have long hypothesized that humanity will someday colonize Jupiter’s moons. Jupiter, being a gas giant, would be difficult to colonize. Ganymede, on the other hand, is slightly larger than the planet Mercury. One of Heinlein’s characters once quoted a Jovian proverb, “Every civilized man has two worlds: his own, and Ganymede.” With NASA returning to the Moon this century and hoping to send manned missions to Mars, human settlements on some of Jupiter’s 80 moons are not impossible.

Ly used old telescope images to spot Jupiter’s 80th moon. The moon is probably only a few dozen miles in diameter.  (Ly posted their data visuals in Imgur.)

Jupiter and Ganymede

Spanning most of the image is the planet Jupiter, its red spot centrally featured. In the lower right, its largest moon Ganymede peaks from behind the planet.
Jupiter and its largest moon Ganymede are shown in this image. Ganymede is slightly larger than the planet Mercury. Meanwhile, Jupiter’s new 80th moon is much smaller, likely only a few dozen miles in diameter. (NASA, ESA, and E. Karkoschka (University of Arizona))

The 1st Planetary Moon Discovered By an Amateur Astronomer

“I’m proud to say that this is the first planetary moon discovered by an amateur astronomer!” they posted June 30 in a message at the Minor Planet Mailing List (MPML), an online community of the world’s leading amateur astronomers.

Using old telescope images, Ly was able spot the unnamed satellite orbiting Jupiter, which is nearly 385 million miles from Earth. The distant planet’s moons include some so small and indistinct they can only be detected about one month of the year, and even then only by a large telescope like the Canada-France-Hawaii telescope at Mauna Kea. Ly used images from this telescope to make his discovery. (Ly posted their data visuals in Imgur.)

Ly’s finding was submitted to scientific journals, but has not yet been published. Ly observed an object originally spotted by NASA in 2003 and thought it was a satellite. Ly calculated its 22-day arc using data from another observatory, the Subaru Telescope, to verify the object was in fact a moon orbiting Jupiter, reported Aubrey Clarke for The Science Times.

Ly’s discovery was possible because observatories post data online for everyone to see and use.

A infographic describing Jupiter and its moon groups.
{image via Carnegie Institution for the Sciences}
A dozen new moons were discovered orbiting Jupiter in 2018. The latest find would add another satellite to the Carme group. (Carnegie Inst. for Science / Roberto Molar Candanosa)

“In the end, I measured a total of 76 observations spanning an arc of 15.26 years (5,575 days),” Ly writes in the MPML message. “The orbit of this Jovian moon is now well-secured for decades to come, so I hereby present to you: Jupiter’s 80th moon, EJc0061 = S/2003 J 24 (provisional designation pending)!”

Congratulations to Kai Ly on discovering Jupiter’s 80th moon. We hope it gets a better official name than EJc0061 = S/2003 J 24. Ly intends to keep searching the data in the hopes of finding other moons. Good luck, Kai Ly!


Susan Macdonald
Susan Macdonald

Susan Macdonald is the author of the children’s book “R is for Renaissance Faire”, as well as 26 short stories, mostly fantasy in “Alternative Truths”, “Swords and Sorceress #30”, Swords &Sorceries Vols. 1, 2, & 5, “Cat Tails” “Under Western Stars”, and “Knee-High Drummond and the Durango Kid”. Her articles have appeared on’s web site, in The Inquisitr, and in The Millington Star. She enjoys Renaissance Faires (see book above), science fiction conventions,  Highland Games, and Native American pow-wows.