Jupiter now has the most documented moons in the solar system

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Jupiter already reigns as king of the planets — it’s the biggest in our solar system. And now the gas giant also has the best-known moons.

Astronomers have observed 12 more moons orbiting Jupiter, bringing its total number of confirmed moons to 92.

The discovery was made during observations by astronomer Scott Sheppard of the Carnegie Institution for Science and its team. They used the Subaru Telescope in Hawaii in September 2021 and the Dark Energy Camera on the Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile in August 2022. The Dark Energy Camera can scan the sky for faint objects .

Jupiter and its natural satellites were aligned with more distant targets that Sheppard and his team were looking for in the Kuiper Belt, a ring of icy objects encircling the sun located beyond Neptune’s orbit on the outskirts of the solar system.

“We searched for new moons around Jupiter by chance as our main survey searches for planets in the outer solar system beyond Pluto,” Sheppard said.

The team could tell the difference between Jupiter and the objects around it versus the distant objects in the solar system, because all objects around Jupiter would move at the same rate as the gas giant. Objects far from the solar system cannot move as quickly as objects moving with Jupiter.

Follow-up observations for the 12 new moons took about a year to confirm, and the team used the Magellan Telescope in Chile to do this work.

None of the moons have a name yet since their discovery was just announced, but the Minor Planet Center will assign them a number in the coming months.

The Minor Planet Center tracks the positions of minor planets, comets, and space rocks. Under the auspices of the International Astronomical Union, the organization is responsible for the identification, designation and orbital data of these celestial objects.

“The International Astronomical Union allows the naming of any moon larger than about 1.5 miles (2.4 kilometers), half of which these new discoveries are larger than that, so they will be given names,” Sheppard said.

Because Jupiter is a bright planet, astronomers have had to deal with the problem of glare and scattered light affecting the space where moons may exist.

The technology facilitates more detailed observation of Jupiter and the area around it.

Sheppard and his team are tracking “many, many more moons around Jupiter,” but they need more observations to confirm and announce their findings.

Finding additional moons around Jupiter and determining their orbits could help identify targets for future missions. The European Space Agency’s Jupiter Icy Moons Explorer, launched in April, and NASA’s Europa Clipper mission, due to launch in 2024, will visit Jupiter and some of its moons this decade. And missions might be able to pass through newly discovered moons on their way.

“These outer moons can only be visited by these spacecraft when they enter Jupiter’s gravitational sphere of influence,” Sheppard said.

“The hope is that if we find enough of them, one will be just near the spacecraft’s path for it to get close-up images. These outer moons are important to understand because this are the last remnants of the population of objects that formed in the region of the giant planets as the rest of the matter was incorporated into the planets.

The region of giant planets is where the largest planets in our solar system are located, and it is now devoid of objects because the planets have swallowed up all the material in the process of formation.

Sheppard and his team believe these moons are remnants of at least seven larger moons that broke apart when they collided with other moons, asteroids or comets. The fracturing of these moons led to the creation of hundreds of smaller moons, Sheppard said.

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The moons are remnants of what was born in the disk of gas and dust around Jupiter after the planet was formed, then captured and pulled most of the material in the orbit of Jupiter. These planet building blocks can open a window into the early years of the solar system.

Sheppard’s team has a knack for finding moons around giant planets in our solar system.

“In total, we have been part of 70 lunar discoveries around Jupiter,” he said by email. “For the other planets, it’s 43 discoveries in Saturn, 2 in Uranus and 1 in Neptune.”

Saturn has 83 moons, Uranus has 27, and Neptune has 14.

The team is also tracking many additional moons around Saturn, but they are harder to locate because the ringed planet is farther from Earth.

“We think Uranus and Neptune also have a large number of small moons, but those planets are even further apart, so it’s even harder to detect the smaller moons around those planets,” Sheppard said.


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