Sheppard, Dave Tholen of the University of Hawaii and Chad Trujillo of Northern Arizona University discovered the most distant known solar system body and were among the first to consider the possibility of a massive, undetected planet beyond Pluto, a claim shared by veteran planet hunder Mike Brown and his colleagues at the California Institute of Technology. This means it crosses paths with the outer retrograde moons and could collide with them.
The inner moons take about a year to circle Jupiter, while the outer moons take twice as long.
As part of that search, Sheppard was using the 4-meter Víctor Blanco Telescope in Chile in March of previous year and realized that Jupiter was right near the part of the sky he wanted to search.
Astronomers think retrograde moons have a different origin story from prograde moons, which travel in the same direction that their planet rotates. Lines point to Valetudo, the newly discovered "oddball" moon. It has an orbit like no other known Jovian moon.
Sheppard said the oddball moon is "likely Jupiter's smallest known moon, being less than 1 kilometer in diameter".
The twelve moons have been broadly clustered into three groups. The lost moons were initially sighted in 2003, but scientists could not define their exact orbits and lost track of them. They named it Valetudo, after a daughter of Jupiter and the Roman goddess of hygiene and personal health. "Head-on collisions would quickly break apart and grind the objects down to dust."Some of Jupiter's moons and moon groupings, including the "oddball", could have formed from collisions like this, according to the statement".
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But the researchers realized that Jupiter happened to be in a spot that allowed them to examine the area around the gas giant for any unknown natural satellites. It has a prograde orbit at a distance where the rest of Jupiter's moons have retrograde orbits.
Eleven are "normal" outer moons, but the 12th, thought to be less than 1km in diameter, has been termed an "oddball" due to its curious orbit.
Sheppard believes it could be Jupiter's smallest, and it has an orbit unlike any other moon around the planet. Sheppard expects there could be even more small moons lurking out there.
Researchers in the United States stumbled upon the new moons while hunting for a mysterious ninth planet that is postulated to lurk far beyond the orbit of Neptune, the most distant planet in the solar system.
For example, the discovery that the smallest moons in Jupiter's various orbital groups are still abundant suggests the collisions that created them occurred after the era of planet formation. Precise calculations were also performed by scientists with the International Astronomical Union's Minor Planet Center, and NASA's Jet Propulsion Laboratory, using the initial observations, to not only confirm that these were not just asteroids passing through their field of view, but also to ensure that astronomers could keep track of these tiny moons and not lose them. Their existence shows that they were likely formed after this gas and dust dissipated.