Astronomers Discover 12 Moons Orbiting Jupiter

July 19, 2018
3 minutes read
Astronomers Discover 12 Moons Orbiting Jupiter

The latest survey of the region around Jupiter revealed 12 moons, raising the number to 79 natural satellites. One of them orbits in a different direction.

On Tuesday, scientists led by Scott S. Sheppard of the Carnegie Institution for Science announced the discovery of twelve new moons around Jupiter. Thus, bringing the total number orbiting the gas giant to 79.

It was a team of U.S. astronomers who in March 2017 became the first to find the moons while they were searching the skies for signs of Planet 9, a hypothesized ninth planet orbiting the sun far beyond Neptune.

According to a press release, confirming the new natural satellites took some time. “It takes several observations to confirm an object actually orbits around Jupiter,” says Gareth Williams of the Harvard-Smithsonian Center for Astrophysics and director of the International Astronomer’s Union’s Minor Planet Center, who calculated the orbits of the new moons. “So, the whole process took a year.”

Most of the moons of Jupiter orbit in the same direction as their neighbors. The moons near Jupiter orbit the gas giant in the same direction as the planet’s rotation – a prograde orbit. The outer moons move in the opposite direction – the retrograde orbit.


Jupiter's moons

The red shows the orbits of nine of the newly discovered moons. You can see the ‘oddball’ Valetudo, in green, moving in the opposite direction. The other two moons are closer to the planet, shown in blue. Credit: Roberto Molar-Candanosa / Carnegie Institution for Science.


The Oddball

One of the newfound celestial bodies has become the main topic.

So, people are calling it an oddball because it orbits Jupiter in the opposite direction of neighboring moons. Scientists call it “Valetudo” for the Roman goddess of health and hygiene and the great-granddaughter of the god Jupiter and it is only about two-thirds of a mile in diameter. Scientists believe Valetudo might be Jupiter’s smallest moon.

Ganymede is the Jupiter’s largest moon and the biggest in the solar system. It has a diameter of about 5,300 kilometers (about 3,300 miles). That’s bigger than the planet Mercury.

“Valetudo is like driving down the highway on the wrong side of the road,” Sheppard tells Sample. “It is moving prograde while all the other objects at a similar distance from Jupiter are moving retrograde. Thus head-on collisions are likely.” But if that collision happens, the impact will be large enough to detect on Earth.

However, the new discovery, especially the oddball, might give astronomers crucial insights to understanding how the moons of Jupiter came to be.

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Thumbnail image: The orbits of the twelve newly discovered moons of Jupiter are shown here in bold. One moon is located in the outer group but orbits in the opposite direction. Credit: Roberto Molar-Candanosa/Carnegie Institution for Science

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