A dozen new moons of Jupiter discovered, including one 'oddball'

Terry Joseph
July 19, 2018

Galileo discovered the first four of Jupiter's moons, all huge, in 1610.

Not only that, but when the orbital characteristics (shape, tilt, and so on) are compared, these nine retrograde moons seem to fall into three groups; that implies that each group used to be a single moon that got smashed somehow, possibly a collision with another moon-sized body.

Nine of the new moons belong to an outer "retrograde" swarm circling against the direction of Jupiter's rotation. "It's also likely Jupiter's smallest known moon, being less than one kilometre (0.62 miles) in diameter".

This new "oddball" moon is more distant and more inclined than the prograde group of moons and takes about one and a half years to orbit Jupiter. Many of Jupiter's outer moons were likely formed by collisions between larger retrograde moons and oddball prograde satellites. Sheppard describes this as "an unstable situation", noting that collisions between two moons are possible due to the 12th moon's unusual orbit. "Head-on collisions would quickly break apart and grind the objects down to dust".

On Tuesday, the International Astronomical Union (IAU) announced the discovery of 10 new moons orbiting Jupiter.

Depending on what survives from any such collision, Jupiter may then have even more moons. That means the revolve around Jupiter opposite from the planet's rotation. Unfortunately, they couldn't find the hypothesized planet using the Blanco 4-meter telescope at Cerro Tololo Inter-American in Chile, but they did manage to unearth a treasure trove of new satellites around our largest planet.

With 67 other known moons flying around Jupiter, there's already a good amount of traffic around the gas planet, as shown in the illustration above. Each takes about two years to circle the planet. In 2017, the group reported two additional Jovian moons.

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"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.

Given their small size, if the moons had existed in the early days of the solar system, the gas and dust that surrounded the Sun at that time would have exerted a strong drag on them, causing them to lose speed and spiral in to crash into Jupiter. "We were able to go a little bit fainter than anyone has been able to go in the past", Scott Sheppard of Carnegie Institution for Science told the Washington Post, "That's why we were able to find these new moons". Others including the oddball are "pro-grade" moons travelling with the planet's spin.

Due to their sizes-one to three kilometers-these moons are more influenced by surrounding gas and dust.

In terms of what it should be called, one of the leading suggestions has been Valetudo, the goddess of health and hygiene, and the great-granddaughter of the Roman god Jupiter. The lost moons were initially sighted in 2003, but scientists could not define their exact orbits and lost track of them.

The moons had not been spotted before because they are tiny.

Scientists believe moons like Valetudo and its siblings appeared soon after Jupiter formed.

"If we do find this planet in the next few years, it would be a pretty wonderful discovery for astronomy".

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