Astronomers Discover 12 New Moons of Jupiter

Jupiter just got a bit more crowded. Astronomers have discovered 12 completely new moons orbiting Jupiter, along with one particular one they have dubbed “oddball,” bringing the total amount discovered to 79. These moons are all fairly small, ranging between from one to three kilometers wide.

With the grand total now up to 79, astronomers classify Jupiter’s moons into a number of categories. The four largest – Europa, Io, Ganymede and Callisto – are generally known as the Galilean moons, after their famous discoverer. Somewhat further out is a “prograde” group which orbits in the identical direction as Jupiter’s spin, while a more distant swarm is a “retrograde” group, orbiting in the opposite direction.

Of the 12 newly discovered moons, two are located in the prograde group. They take a little under a year to orbit Jupiter, and given the similarities in distance and angle of their orbits, objects in this particular group in general are considered to be the destroyed remains of a single larger moon.

Nine of the new moons are out in the retrograde group, where they orbit roughly once every two years. Objects within this group are believed to have originated from three larger moons that have been ripped apart by collisions.

Then there is one strange moon that astronomers are calling Valetudo, which is moving with Jupiter’s spin, like the two inner moons. Which means it is moving in the opposite direction of all the other moons within the same region. “It’s basically driving down the highway in the wrong direction,” Scott Sheppard, an astronomer at Carnegie who led the discovery team, explains. “That’s a very unstable situation. Head-on collisions are likely to happen in that situation.”

The new celestial satellite Valetudo is named after the Roman goddess of health and hygiene. New Jupiter moons are actually named after Roman gods associated with Jupiter. Valetudo is Jupiter’s great-granddaughter. And adorably, Sheppard chose Valetudo as a nod to his girlfriend, whom he describes as a “very cleanly person.”

Astronomers at Carnegie Institution for Science first discovered these moons in March 2017, in conjunction with two others which were already confirmed in June of last year. The team initially discovered all 12 moons using the Blanco 4-meter telescope in Chile.

Astronomers had surveyed this area before, but Sheppard’s team reasoned that the DECam would spot smaller, darker objects that older instruments overlooked. The plan was simple: subtract previous images of the planet and its surroundings from those captured by their powerful new camera. Anything left stood a good chance of being a never-before-seen object—and, potentially, a Jovian satellite.

“As our technology gets better and better, we’re able to look fainter and fainter, so we’re discovering smaller and smaller moons,” said Sheppard.

Sheppard and his team hope to further explore what could’ve caused these moons to form in order to get a better understanding of how the planet itself formed — and ultimately, more about how the rest of our solar system came to be.