They first spotted the 12 new moons in the spring of 2017, but they had to conduct several more observations before they could confirm that the moons actually orbited Jupiter, according to Gareth Williams of the International Astronomical Union's Minor Planet Centre. The new ones were found because technology has gotten better and better over the years. The find pushes Jupiter's total moon count to 79, the most of any planet in our solar system.
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. "We were serendipitously able to look for new moons around Jupiter while at the same time looking for planets at the fringes of our solar system".
Because Jupiter moves across the sky at a known speed, anything nearby moving at the same speed in the same direction becomes a candidate for a moon - but confirmation is a time-consuming process, Sheppard explained to ScienceAlert. Jupiter is not in the frame and is off to the upper left. Even though a dozen new moons is a pretty good haul, Sheppard expects that more searching will turn up even more moons. For the other 11 moons, Sheppard said they might let the public help out.
"With the discovery of Valetudo, it seems the collisions that broke apart the retrograde moons were between other prograde Jupiter moons, like Valetudo", Sheppard told ScienceAlert. It's just 1 kilometer wide, which makes it Jupiter's smallest moon, and takes a year and a half to orbit the planet. "They're going around the planet in the opposite direction that Jupiter rotates", Sheppard says. One of the moons, Valetudo (between orange markers), can be seen in these images. It's out where the outer, retrograde moons are, but it's orbiting Jupiter in the prograde direction, driving into the oncoming traffic.
The tiny moon's orbit takes it both inside and outside of where the other new moons orbit, putting it at a high risk of colliding with them. Those eleven moons are probably remnants of larger bodies that got broken up in collisions.
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.
Because the new moons are a few kilometers in size, the team thinks that the impacts that created the satellites likely took place after the era of planet formation ended. That's a lot of moons.
Sheppard, Chad Trujillo of Northern Arizona University and David Tholen of the University of Hawaii are on a quest to find as many faint, distant objects on the edge of the solar system as they can.
Jupiter's moons are arranged in a specific pattern that the giant planet has worked out over time.
Sheppard and his team already proposed a name for the rebel moon.
Once they finish running and analyzing the simulations, the team plans to publish the results in early 2019.
Valetudo, as the team calls this oddball moon, is named after the Roman goddess of health, cleanliness and hygiene.