How many moons orbit Jupiter? Currently, astronomers have confirmed 79. Yet, research from three University of British Columbia astronomers suggests hundreds more may exist.
Moons in our solar system are being discovered regularly. In October 2019, scientists announced 20 new moons around Saturn. Shortly before, another team confirmed 12 additional satellites around Jupiter, raising the total to 79—with five recently named. But are there even more?
Quite possibly. Researchers from the University of British Columbia project up to several hundred irregular satellites around Jupiter with radii exceeding 400 meters. Their forthcoming study, set for publication in The Planetary Science Journal, awaits peer review.
To derive this estimate, the team analyzed 2010 observation archives from the Canada-France-Hawaii Telescope. They processed images of Jupiter's surroundings in 126 configurations, accounting for every plausible speed and direction a potential moon might traverse the sky, as detailed by Sky & Telescope.
This effort revealed 45 new faint moving objects—prime candidates for irregular satellites. Having surveyed just one square degree of sky, the researchers extrapolated their results across Jupiter's full vicinity, predicting around 600 such moons.
These irregular moons occupy distant, eccentric, and often retrograde orbits, moving opposite the planet's rotation. Unlike regular moons formed by accretion in a protoplanetary disk like Io, Ganymede, Europa, and Callisto, irregulars are captured objects from elsewhere in the solar system.
Confirmation awaits, with the team eyeing the Vera C. Rubin Observatory, slated for operation in one to two years. This powerful instrument will scan for small solar system bodies, potentially unveiling these hidden moons.
