The Latest: On Jul. 17, 2018, scientists announced they had discovered 12 new moons orbiting Jupiter. That raised Jupiter’s total number of moons to 79—the most of any planet in the solar system. Fifty-three of the moons are confirmed and named; the other 26 are awaiting official confirmation of discovery before they are named.
The team first spotted the moons in the spring of 2017 while they were looking for very distant solar system objects as part of a hunt for a possible massive planet far beyond Pluto. “Our other discovery is a real oddball and has an orbit like no other known Jovian moon,” team leader Scott Sheppard said. “It’s also likely Jupiter’s smallest known moon, being less than one kilometer in diameter”.
NASA Science: Solar System Exploration