Ten more moons have been confirmed to orbit around Jupiter, bringing the planet’s total known satellite count to 79.
That’s the highest number of moons of any planet in the Solar System. And these newly discovered space rocks are giving astronomers insight as to why the Jupiter system looks like it does today.
Astronomers at Carnegie Institution for Science first found these moons in March 2017, along with two others that were already confirmed in June of last year.
The team initially found all 12 moons using the Blanco 4-meter telescope in Chile, though finding these objects wasn’t their main goal.
Instead, they were searching for incredibly distant small objects — or even planets — that might be lurking in our Solar System beyond Pluto.
But as they searched for these fringe space rocks, they decided to take a peek at what might be lurking around Jupiter at the same time.
Now, the moons they found have been observed multiple times, and their exact orbits have been submitted for approval from the International Astronomical Union, which officially recognizes celestial bodies.
These moons are all pretty tiny, ranging between less than a mile and nearly two miles wide. And they break down into three different types. Two orbit closer to Jupiter, moving in the same direction that the planet spins.
Farther out from those, about 15.5 million miles from the planet, there are nine that revolve in the opposite direction, moving against Jupiter’s rotation.
But in this same distant region, one strange moon that astronomers are calling Valetudo is moving with Jupiter’s spin, like the two inner moons.
That means it’s going in the opposite direction of all the other moons in the same area. “It’s basically driving down the highway in the wrong direction,” Scott Sheppard, an astronomer at Carnegie who led the discovery team said.
“That’s a very unstable situation. Head-on collisions are likely to happen in that situation.”
Valetudo isn’t the only moon of Jupiter that acts this way. Another moon called Carpo also orbits far out from Jupiter, moving in the opposite direction of many other moons in the area.
However, Valetudo orbits much farther away than Carpo, and it may actually be the smallest moon Jupiter has.
Now with this discovery, astronomers think it’s good evidence that moon-on-moon collisions have happened in Jupiter’s past, and these are responsible for the lunar landscape around the planet today.
“Valetudo, at just 1 kilometer across, is probably the last remnant of a much larger moon that’s been ground down into dust over time,” says Sheppard.
Finding moons around Jupiter can be tough. As the biggest planet in our Solar System, it has a very large area of influence, so there’s a lot of space where moons could potentially be.
It’s difficult to search that area in a timely manner with a telescope. “It’s like looking through a straw, and you’re just covering as many points around Jupiter as you can looking for these things,” says Sheppard.
And since Jupiter is so large, it reflects a whole lot of light. That means there can be a lot of glare when searching for super faint moons around the planet.
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