The new find boosts Jupiter's moon count to 79, easily making it the most populous place for moons in our solar system.
Sheppard's team found the moons while searching for Planet Nine, a distant, undiscovered planet thought to be altering the paths of objects in our solar system.
A research team from the Carnegie Institution for Science, the University of Hawaii and Northern Arizona University was looking in 2017 for very distant objects in our solar system, well beyond Pluto.
The team is calling one of the new moons an "oddball" because of its unusual orbit.
The orbit of a dozen previously unknown moons around Jupiter are shown here, including the "oddball" discovery, Valetudo. Two of those are part of Jupiter's group of inner prograde moons, meaning that they orbit in the same direction as the planet rotates.
"The question is, are there more Valetudos, weird objects that have these different orbits", Sheppard said.
And he thinks Jupiter might have even more moons just as small waiting to be found.
Outside the orbits of the prograde moons is the largest group, the retrograde moons, which orbit around Jupiter in the opposite direction to the planet's spin. Only the two innermost planets in the solar system, Mercury and Venus, have none.
The existence of so many small satellites suggests that they arose from cosmic collisions after Jupiter itself formed, more than 4 billion years ago. "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".
Astronomers suspect that the retrograde moons may be the remains of larger moons that were destroyed in head-on collisions with prograde objects. They are also part of a larger group of small moons thought to be the left-over remnants of a once larger moon.
All less than two miles wide, the moons are all very small which is why they have only now been identified thanks to more sensitive telescopes.
In terms of what it should be called, one of the leading suggestions has been Valetudo, the goddess of health and hygiene, and the great-granddaughter of the Roman god Jupiter.
Jupiter isn't particularly lacking when it comes to moons orbiting it.
Due to their sizes-one to three kilometers-these moons are more influenced by surrounding gas and dust.
It will appear as the fourth brightest object in the sky behind the moon, Mars and Venus.
Sheppard said Jupiter and Saturn may actually have a similar number of moons, with some of the latter's smaller ones not yet detected. There are two moons close to the planet that are spinning in the same direction. But astronomers can't wait a year to make the follow-up observations, because the objects become lost or hard to properly associate with the same object, so it's necessary to track the candidate moons multiple times over the course of a year.