12 new moons were discovered orbiting Jupiter, and one’s an ‘oddball’

Jupiter got 12 new moons on Tuesday, July 17. Well, not exactly. Those dozen moons have, of course, always been in Jupiter’s orbit, but it was only this week that researchers from the Carnegie Institution for Science announced their discovery. The addition of these 12 brings the total number of moons (that we know of) to a whopping 79. As you might imagine, that’s far more than any other planet in our solar system can boast.

While the research team has suspected the existence of these 12 moons for about a year, it takes several observations in order to confirm that an object is, in fact, orbiting Jupiter. As such, the team took their time in confirming the new Jovian moons.

Scientists made their latest discovery when they were actually looking for another extraterrestrial body — Planet X, the planet that is suspected to exist somewhere beyond Pluto.

“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,” team leader Scott S. Sheppard said in an announcement. Of the 12 new moons discovered, 11 are described as normal moons, while the other is an “oddball.”

What makes it weird? Apparently, it’s just 1 kilometer wide, which means it’s the smallest moon scientists have discovered to date orbiting the planet, and it takes a full year and a half to make a complete trip around Jupiter. Moreover, its orbit crosses that of other moons in retrograde (those that travel in the opposite direction of Jupiter’s rotation), which is to say that at some point, multiple moons could collide. “This is an unstable situation,” Sheppard noted. “Head-on collisions would quickly break apart and grind the objects down to dust.”

This discovery could actually give scientists clues into the formation of moons and planets as a whole. As the team noted in its announcement, “Elucidating the complex influences that shaped a moon’s orbital history can teach scientists about our Solar System’s early years.” In this case, determining that there are still several small moons surrounding Jupiter suggests that they were actually created after the planets were formed.