Published: Wed, July 18, 2018
Sci-tech | By Carrie Guzman

Twelve new moons orbiting Jupiter - one may collide with the others

Twelve new moons orbiting Jupiter - one may collide with the others

Astronomers searching for a planet beyond Pluto discovered instead a dozen new moons orbiting Jupiter. That brings the total number of Jovian moons to 79. The orbits of the new moons are marked with thicker curves. Given their distance and angle from Jupiter, they are also most likely pieces of a once-larger moon.

A look at Jupiter's new moons.

Nine of the dozen moons are well away from Jupiter and have retrograde orbits, meaning they go around the planet in what we'd think of as the "wrong direction". He and his team have been photographing the skies with some of today's best telescope technology, hoping to catch sight of this mysterious ninth planet.

"What astonishes me about these moons is that they're the remnants of what the planet formed from", he said. 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.

"This is an unstable situation", said Sheppard. "Head-on collisions would quickly break apart and grind the objects down to dust".

They are also believed to be fragments of a larger moon that was broken apart and take just under a year to circle Jupiter. Jupiter is not in the frame, but off to the upper left.

The researchers, from the Carnegie Institution for Science in Washington, DC, picked out one of the 12 moons as an "oddball". But Juno is too close to the huge planet and its field of view is too small to capture images of the planet, Sheppard said. They saw a new group of objects moving around the giant gas planet but didn't know whether they were moons or asteroids passing near Jupiter.

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Two previously undetected moons were found closer in, part of a group that orbits in the same "prograde" direction as Jupiter's rotation.

This moon, now called Valetudo, moves in a prograde motion, though it is slightly inclined compared to the orbits of the other moons. The 7 new retrograde moons join 45 other satellites that take 2-3 years to orbit. It's out where the outer, retrograde moons are, but it's orbiting Jupiter in the prograde direction, driving into the oncoming traffic.

The moons Sheppard spied are farther-flung and tiny, each no more than two miles in diameter. 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. To check whether this could have happened, the researchers are working on supercomputer simulations of these orbits to calculate how many times an object with Valetudo's orbit could have collided with the retrograde moons in the solar system's lifetime. That's a lot of moons. A prograde satellite may simply have been floating through the solar system before being captured by Jupiter. "Magnificent desolation", Sheppard says, is the ideal. "They were like vacuums, they sucked up all that material and that created the planets", Sheppard explains.

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

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.

And then there's the oddball moon.

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