Discoveries boost Jupiter’s retinue to 79 moons - including a wrong-way oddball

Eloise Marshall
July 20, 2018

The work was led by Scott Sheppard, a researcher at the Carnegie Institution for Science who studies small bodies in the solar system and the formation of planets and stars. "It's going to slap into something".

Sheppard adds that the moons may be leftovers from early solar system objects. "It is likely one of these spacecraft will fly by one of these distant Jupiter moons to get a close-up view".

"The giant planets formed out of material that used to be in that region". If you said four, you might be Galileo.

PHOTO: An animation shows the movement of a tiny moon of Jupiter that researchers are calling Valetudo. Confirmation came with help from a variety of observatories, including the 6.5-metre Magellan telescope at Carnegie's Las Campanas Observatory in Chile, the 4-metre Discovery Channel Telescope at Lowell Observatory in Arizona, the 2.2-metre University of Hawaii telescope and the 8-metre Subaru and Gemini Telescopes, also in Hawaii. These satellites are part of a large group of moons that orbit in retrograde far from Jupiter. Those moons are also believed to be remnants of a larger moon that was smashed to pieces.

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.

The observations revealed a dozen previously unknown moons circling the gas giant.

Astronomers say they've discovered another 12 moons orbiting Jupiter.

As a whole they're not so unusual or remarkable, except, perhaps, for that rogue, Valetudo. 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.

Illustration of the new moons orbiting Jupiter
Astronomers discover 12 new moons orbiting Jupiter - one on collision course with the others

The effect of opposition is similar to the effect of the full moon seen once a month when Earth is positioned directly between our natural satellite and the sun.

"These objects started orbiting Jupiter, instead of falling into it".

The inner moons take about a year to circle Jupiter, while the outer moons take twice as long. These all travel in retrograde, or the opposite of Jupiter's rotation, while two more, also though to be moon remnants, travel in prograde.

This means, unlike those closer to Jupiter, it crosses the outer retrograde moons. "The only thing that we know at the moment are the orbits and the approximate size", Williams said.

The remaining moon is less than a kilometer across, further out than the two conventional moons and has a 1.5-year orbit-and the orbit is inclined. Sheppard said another collision will likely happen during the solar system's lifetime.

Sheppard and his colleagues speculate that Valetudo was probably once much larger, but was ground down, over the course of billions of years, as a result of collisions. They are about one to two kilometers (miles) across, said astronomer Gareth Williams of the International Astronomical Union's Minor Planet Center.

Astronomers first spotted the moons in the spring of 2017 while they were searching for a possible massive planet beyond Pluto.

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