Now, Edward Ashton, Matthew Beaudoin, and Brett Gladman (University of British Columbia, Vancouver) have detected about four dozen possible new Jovian moons that are even smaller. Extrapolating from the sky area they have searched (about one square degree), they conclude that there could be some 600 of these tiny objects orbiting the giant planet.
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This method revealed 52 objects down to magnitude 25.7, corresponding to diameters of some 800 meters. Seven of the brighter finds turned out to be known irregular satellites of Jupiter; the others are almost certainly retrograde Jovian moons, which orbit the planet in the direction opposite its rotation. A paper describing the results has been accepted for publication in The Planetary Science Journal (full preprint available here).
If this sensitive one-square-degree “pencil-beam” search already yields 45 formerly unknown moons, the researchers estimate that the total number of satellites within this size range must be around 600. The current official number of Jovian moons is 79.
Sheppard (whose team found 20 new satellites of Saturn last year) is not surprised by the new result. “We used a similar shift and stack technique for our Jupiter moon discoveries that were announced in 2018,” he says. “In our paper, we also mentioned detections that we could not confirm as moons, because we didn’t observe them for the months and years required to reliably determine their orbits.”
https://skyandtelescope.org/astronomy-news/jupiter-could-have-600-moons/(though some of the 45 may be the 16 Jupiter moons that Sheppard announced after that 2020 article:
https://en.wikipedia.org/wiki/Timeline_of_discovery_of_Solar_System_planets_and_their_moons )
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