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Astronomers discover 10 new moons for Jupiter

19 July 2018

The discovery brings Jupiter's total number of known moons to a whopping 79 - the most of any planet in our Solar System.

Before Sheppard's team conducted their survey, there were 69 known Jovian moons, but there's always been reason to believe there are quite a few more.

"Understanding these moons helps us understand what the planets were originally made from", Sheppard told ABC News via email, adding that the moons are "likely half ice and half rock". Two of the newly discovered moons were found among these prograde moons, and take a little less than a year to go around in their orbit once.

But the "oddball" moon has really excited the astronomers.

"It takes several observations to confirm an object actually orbits around Jupiter", Gareth Williams of the International Astronomical Union's Minor Planet Center explained in a news release.

Beyond these is a group known as the "prograde" moons - more tiny, irregular satellites, all of which travel around Jupiter in the same direction that the planet rotates (counter-clockwise, in the view shown below).

They also have a retrograde orbit, or the opposite direction to the spin of Jupiter on its axis.

That also includes one that they've referred to an "oddball", which is flying in the opposite direction to many of Jupiter's other moons and measures just 1km in size. Sheppard said another collision will likely happen during the solar system's lifetime. Nine of the new satellites orbit in a distant swarm of outer moons that are thought to be leftover from a series of collisions that might have involved what were once three larger bodies. "What these other objects were has been a mystery".

Astronomers Just Announced The Discovery of 12 New Moons Around Jupiter
Astronomers discover 10 new moons for Jupiter

Researchers found the new moons thanks to a telescope upgrade.

These two groups of prograde and retrograde moons consist of "irregular" satellites, or moons whose orbits have irregular, or noncircular, shapes.

Two of them are pretty straightforward.

Scott Sheppard: "We believe these objects were probably captured by Jupiter a long time ago and they are grouped in their orbits".

It has most likely collided with other moons, breaking it down into the fragment it is today. One possibility is NASA's Europa moon mission planned in the late 2020s or early 2030s. They're calling one moon an "oddball" because of its unusual orbit. And with Jupiter being the biggest planet in our solar system, astronomers need to be able to see as much of the space around it as possible.

Valetudo orbits Jupiter in the same direction that the planet spins, but a bunch of other small moons share the same orbital path while travelling in the opposite direction.

In fact, Sheppard and his team at Carnegie think that this moon could be all that's left of a previous collision in orbit around Jupiter. "Not because of its orbit, but rather because it's so small". They're thought to have formed after the gas and dust from the earliest stages of planetary formation had dissipated. Distant solar system objects can't move that quickly. Sheppard expects there could be even more small moons lurking out there.

The newly discovered moons await naming, a task for which the public may be enlisted, so it's a good idea to brush up on the IAU's naming rules for Jovian moons - and which names have already been taken.

Astronomers discover 10 new moons for Jupiter