One of the new moons in the outer group is particularly unique, according to astronomer Scott Sheppard at the Carnegie Institution for Science, who led the team that first spotted the moons past year.
However, the researchers found that Jupiter-like planets are apparently not less common around stars hosting super-Earths than they are stars without super-Earths, but more common.
While the hunt for this planet continues, this major moon haul could help piece together more parts of the jigsaw that is the history of the solar system's earliest years, as elucidating the complex influences that shaped a moon's orbital history can help reveal this.
The Carnegie Institution team, led by Scott Sheppard, didn't set out to find even a single new Jovian moon. "We know nothing, really, more than that".
In March 2017, Jupiter was in the ideal location to be observed using the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile, which has the Dark Energy Camera and can survey the sky for faint objects. That brings the total number of Jovian moons to 79. Nine of them have retrograde orbits, going in the opposite direction to Jupiter's spin. And more than a third of those belong to a single planet: Jupiter.
Closest to the planet are the four small "inner irregulars", named Metis, Adrastea, Amalthea and Thebe. The largest Galilean moon, Ganymede, is bigger than the planet Mercury. Nine others orbit with Jupiter's outer retrograde moons in the opposite direction.
Among them, seven orbit Jupiter at a considerable distance of about 20 million kilometres, while the remaining two are much closer. Thus, they orbit in the same direction as the planet.
"Our other discovery is a real oddball and has an orbit like no other known Jovian moon", Sheppard explained. The 12th and final moon, however, has instead been labeled an "oddball" by the team.
The so-called "oddball" has such a unique orbit that it is at risk of smashing into the other moons - a cosmic collision that could risk wiping the space rocks out. While the retrograde moons orbit in a clockwise direction, Valetudo travels in a counter-clockwise direction.
Because Valetudo's orbit crosses the orbits of some of the outer retrograde moons, it's possible that it suffered a head-on collision in the past.
A head-on collision between two moons would "grind the objects down to dust", he added.
According to the team, these moons, and especially Valetudo, likely did not form at the same time as Jupiter, but rather are probably the tiny remnants of larger objects that suffered numerous collisions as they circled the gas giant. Most big objects in the solar system all orbit the Sun and spin in the same sense (the motion is counterclockwise when looking down from above the Earth's north pole).
Overall, this was a tough, but very rewarding discovery. Several other telescopes also confirmed those observations.