Twelve new moons orbiting Jupiter have been discovered. This brings Jupiter’s total number of confirmed moons 79, the most of any planet in our Solar System.
Scott Sheppard and his team from Carnegie University first observed the moons in 2017 while looking for “Planet X”, a massive planet that may exist beyond Pluto in the deep reaches of our solar system. The discovery was a happy accident.
Jupiter just happened to be in the sky near the search fields where we were looking for extremely distant Solar System objects, so 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. – Scott Sheppard
Out of the twelve, nine of the new moons are part of a distant ring of retrograde outer moons that orbit in the opposite direction of Jupiter’s spin rotation, each taking about 2 years to complete one circuit. Two of the new discoveries are part of a closer, inner group of moons in a prograde orbit moving in the same direction as the planet’s rotation and taking a little less than a year to travel around Jupiter. These newly discovered moons are in distinct orbital groupings and give us an idea of the violent processes that created them. Each moon group has similar orbital distances and paths around Jupiter, because of these factors they are thought to be the remnants of larger bodies that broke apart during collisions with asteroids, comets, or other planetary bodies.
Photo By Roberto Molar-Candanosa, courtesy of Carnegie Institution for Science.
The final moon is said to have very distinct properties. “Our other discovery is a real oddball and has an orbit like no other known Jovian moon” according to Sheppard. They are planning to name it “Valetudo”, after one of the Greek god Jupiter’s descendants. This new “oddball” moon is more distant than the first “Gailiean” and second “prograde” groups of moons and takes about one and a half years to orbit Jupiter. Due to its sightly elliptical orbit, this new moon has an orbit that crosses the outer retrograde moons. The equivalent of driving into oncoming traffic creates what Sheppard calls “an unstable situation.” A collision between this moon and one of the others would more than likely see both objects destroyed.