This discovery brings the total number of known Jovian moons to 79 - the most of any planet in the Solar System.
The team that discovered the moons was searching for a hypothetical massive planet that might exist at the far fringes of our solar system, often referred to as Planet Nine or Planet X. If there's another planet orbiting the Sun way, way far out - the so-called Planet Nine - then its gravity may affect the orbits of these KBOs, allowing astronomers to figure out where this possible planet is. His team at Carnegie, along with collaborators at the University of Hawaii and Northern Arizona University, was hunting for objects far beyond Pluto.
They are also believed to be fragments of a larger moon that was broken apart and take just under a year to circle Jupiter.
It took a year for their orbits to be confirmed with a series of other telescopes in the United States and Chile. Two of the 12, on the other hand, are found in a closer group that orbits Jupiter in prograde, which is the same direction of the planet's rotation. While the team did discover 12 new moons, two were announced past year.
The final discovery is classified as an "oddball" as it has an orbit unlike any other Jovian moon. Nearly all of Jupiter's prograde moons are believed to be fragments of a larger moon that broke apart.
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Jupiter's biggest moon, Ganymede, also has an underground salt ocean - although this ocean may be too salty to be habitable. Sheppard believes it could be Jupiter's smallest, and it has an orbit unlike any other moon around the planet.
Nine of the found moons are part of the distant retrograde group that orbit in the opposite direction of Jupiter's spin rotation, according to Carnegie Institution for Science.
This means, unlike those closer to Jupiter, it crosses the outer retrograde moons. Sheppard said another collision will likely happen during the solar system's lifetime. "Head-on collisions would quickly break apart and grind the objects down to dust", Dr. Sheppard said. "Most of the small objects that helped build the planets we see today were incorporated into the planets themselves, and these moons are all that remains", Sheppard wrote.
This survivor could be the last remnant of a once-larger prograde moon that collided with an object to create the retrograde moons.
Europa, one of Jupiter's larger moons, casts a shadow on the planet's surface. One moon is located in the outer group but orbits in the opposite direction. It has a prograde orbit at a distance where the rest of Jupiter's moons have retrograde orbits. Their existence shows that they were likely formed after this gas and dust dissipated.
Using the Blanco 4-meter telescope at Cerro Tololo Inter-American in Chile, with its highly-sensitive Dark Energy Camera, however, gave the team a distinct advantage. Jupiter is not in the frame, but off to the upper left.
The oddball is thought to be Jupiter's smallest moon; it measures roughly 3,000 feet across.