Saturn surpasses Jupiter to become new moon king

Pablo Tucker
October 8, 2019

The team says that the orbits of these new moons make it possible to narrow down a window for when they formed. Carnegie is now hailing Saturn as the new "king of moons".

Saturn image is courtesy of NASA/JPL-Caltech/Space Science Institute.

"We are now only able to find moons that are a few miles in size around Saturn because the planet is so far away".

Thanks to a team led by famed astronomer Scott S. Sheppard 20 new moons have been discovered orbiting Saturn.

As you might recall from a year ago, Sheppard was involved in the discovery of 12 additional moons around Jupiter, bring the Jovian giant's total to 79.

The announcement was officially made by the International Astronomical Union's Minor Planet Center. By contrast, Saturn's 20 new moons are minuscule, each barely 3 miles (5 kilometers) in diameter. Most of them, 17 in fact, orbit in a retrograde motion - opposite to the direction of Saturn's rotational axis.

The new moons were slotted into three distinct categories depending on the angles at which they orbit around Saturn.

Two of the moons are part of a group of moons called the Inuit group, whose original members were discovered by Canadian astronomers and named by team member John Kavelaars, now at the Dominion Astrophysical Observatory in Victoria, and Inuit storyteller and children's author Michael Arvaarluk Kusugak. Two of the moons take about two years to orbit, while the other 18 take more than three years to complete an orbit.

"Studying the orbits of these moons can reveal their origins, as well as information about the conditions surrounding Saturn at the time of its formation", Sheppard explained.

Mini-moons around planets are hard to spot as more powerful telescopes are needed to find them. And for the Gallic-group moon ... you guessed it: a mythological Gallic giant.

The remaining prograde moon was placed in the Gallic group (shown in green), but it's much farther out than previously known Gallic moons, so this designation may not stick, according to the Carnegie release.

One of the prograde satellites has a tilted orbit at 36 degrees, similar to the other known inner prograde moons in the Gallic group.

So, as of October 7, 2019, a new contest has opened up on the Carnegie Science website, for the public to submit names for these 20 newfound moons. In a similar vein, a gas and dust ring likely surrounded Saturn during its formation which gradually accreted to form its moons. By comparing images taken over hours and days, the algorithms distinguished between stationary stars and galaxies and moons that hurtled around the planet.

"This kind of grouping of outer moons is also seen around Jupiter, indicating violent collisions occurred between moons in the saturnian system or with outside objects such as passing asteroids or comets", said Dr Sheppard. But the newly discovered moon is farther out than the others.

Astronomers have pretty much completed the inventory of moons, Dr Sheppard said, adding that future larger telescopes would be needed to see anything smaller.

A gif of the discovery images for the newly found very distant prograde moon of Saturn.

At the birth of the solar system, vast amounts of dust and gas circling the sun coalesced into the eight known planets. "It is believed that a similar gas-and-dust disk surrounded Saturn during its formation".

In addition to Sheppard, the observing team included UCLA's David Jewitt and the University of Hawaii's Jan Kleyna.

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