Jupiter's moon count reaches 79, including tiny 'oddball'

Jupiter's moon count reaches 79, including tiny 'oddball'

Dr Sheppard and colleagues first spotted the moons in spring past year while they were looking for very distant Solar System objects as part of the search for the suspected planet on the fringes.

They were first spotted a year ago by a team of astronomers originally on the hunt for the elusive Planet Nine, a hypothetical body speculated to exist beyond Neptune. With a total of 79 moons, Jupiter is now the most lunar-rich planet in the solar system. Sheppard describes this as "an unstable situation", noting that collisions between two moons are possible due to the 12th moon's unusual orbit.

"It's allowed us to cover the whole area around Jupiter in a few shots, unlike before, and we're able to go fainter than people have been able to go before", says Sheppard.

"We had to observe the new candidate Jupiter moons again a month later and again a year later to confirm they were actually orbiting Jupiter and thus were moons of Jupiter", he said.

Jupiter's southern hemisphere is pictured by NASA's Juno spacecraft on the outbound leg of a close flyby of the gas-giant planet in an image released on July 2, 2018.

All the newly identified moons are relatively small, ranging in size from about six-tenths of a 1km to 4km.

It's likely that even more small moons are still waiting to be found. Astronomers think these moons may have originally been part of one larger moon that broke apart, according to the Carnegie statement.

Now that they've been accounted for, the total number of objects found orbiting Jupiter has gone up to 79, though scientists believe there could be around 100 in total. One of the moons, Valetudo (between orange markers), can be seen in these images.

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PALCA: Many of Jupiter's moons form from the same spinning disk of stuff that eventually coalesce to form the planet. It's believed that numerous tiny moons around Jupiter were once much larger, having broken up over time due to the stress of gravity or perhaps even collisions with each other, resulting in the smaller objects we see today. As such, the orbit crosses those of the more distant retrograde moons, raising the possibility of a possible head-on collision at some point in the future.

Our solar system's oldest and biggest planet, Jupiter, has many moons.

Finding lots of these small moons also tells us about conditions in the early solar system. Yet it's orbiting in the same direction as the planet, against the swarm's traffic.

The team believes Valetudo might be a fragment of a larger moon, broken off in a collision with a larger retrograde moon, resulting in something like the retrograde groupings observed.

The fact that these smaller moons exist today is evidence that any collisions that created them happened after this era of planet formation. By contrast, retrograde moons were probably objects that once were wandering around the solar system and got snared by Jupiter's gravity.

The observations revealed a dozen previously unknown moons circling the gas giant. One of the finds is an oddball that moves in the opposite direction from its neighbors.

The IAU requires moons of Jupiter to have names related to the Roman god Jupiter.

"It's basically driving down the highway in the wrong direction", Sheppard said. Valetudo was known for being the goddess of health and hygeine.

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