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Astronomers find 20 new moons orbiting Saturn

AP, October 9, 2019 7:00PM Kids News

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Combined images of Saturn and some of its 82 known moons. media_cameraCombined images of Saturn and some of its 82 known moons.


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The solar system has a new winner in the most-moons category.

Scientists have found 20 new moons around Saturn, giving the ringed planet a total of 82. That beats Jupiter and its 79 moons.

“It was fun to find that Saturn is the true moon king,” said astronomer* Scott Sheppard of the Carnegie Institution for Science in Washington DC in the US.

Jupiter, however, keeps its crown as the planet in our solar system with the biggest moon. Jupiter’s Ganymede is almost half the size of Earth. Our Moon, orbiting Earth, has a diameter* of 3474.2km. By contrast, Saturn’s 20 new moons are tiny, each barely 5km in diameter.

Image 2 NASA's Hubble Space Telescope has caught Jupiter's moon Ganymede playing a game of "peek-a-boo." In this crisp Hubble image, Ganymede is shown just before it ducks behind the giant planet. Ganymede completes an orbit around Jupiter every seven days. Because Ganymede's orbit is tilted nearly edge-on to Earth, it routinely can be seen passing in front of and disappearing behind its giant host, only to reemerge later. Composed of rock and ice, Ganymede is the largest moon in our solar system. It is even larger than the planet Mercury. But Ganymede looks like a dirty snowball next to Jupiter, the largest planet in our solar system. Jupiter is so big that only part of its Southern Hemisphere can be seen in this image. Hubble's view is so sharp that astronomers can see features on Ganymede's surface, most notably the white impact crater, Tros, and its system of rays, bright streaks of material blasted from the crater. Tros and its ray system are roughly the width of Arizona. The image also shows Jupiter's Great Red Spot, the large eye-shaped feature at upper left. A storm the size of two Earths, the Great Red Spot has been raging for more than 300 years. Hubble's sharp view of the gas giant planet also reveals the texture of the clouds in the Jovian atmosphere as well as various other storms and vortices. Astronomers use these images to study Jupiter's upper atmosphere. As Ganymede passes behind the giant planet, it reflects sunlight, which then passes through Jupiter's atmosphere. Imprinted on that light is in media_cameraJupiter’s moon Ganymede just visible behind Jupiter. Composed of rock and ice, Ganymede is the largest moon in our solar system and is even larger than the planet Mercury. This photo was taken by NASA’s Hubble Space Telescope.

Dr Sheppard and his team used a telescope in Hawaii to spot Saturn’s 20 new moons in the past couple of months. About 100 even tinier moons may be orbiting Saturn, still waiting to be found, he said.

Astronomers have pretty much completed the inventory* of moons as small as 5km around Saturn and 1.6km around Jupiter, according to Dr Sheppard. Future larger telescopes will be needed to see anything smaller.

It’s harder spotting mini moons around Saturn than Jupiter, Dr Sheppard said, given how much farther away from Earth Saturn is.

“So seeing that Saturn has more moons even though it is harder to find them, shows just how many moons Saturn has collected over time,” he wrote in an email. These baby moons may have come from larger parent moons that broke apart right after Saturn formed.

The Cassini spacecraft has captured a striking image of Saturn's moons Dione and Tethys passing each other across the planet's ring system. media_cameraSaturn’s moons Dione and Tethys passing each other, with the planet’s ring system just visible at the bottom. This photograph was taken by the Cassini spacecraft.

Seventeen of Saturn’s new moons orbit the planet in the opposite, or retrograde, direction. The other three circle in the same direction that Saturn rotates. They’re so far from Saturn that it takes two to three years to complete a single orbit.

“These moons are the remnants* of the objects that helped form the planets, so by studying them, we are learning about what the planets formed from,” he wrote.

Just last year, Dr Sheppard found 12 new moons around Jupiter. The Carnegie Institution had a moon-naming contest for them; another is planned now for Saturn’s new moons.

- media_cameraSaturn’s moons Dione (front) and Enceladus photographed by the Cassini spacecraft in 2015. Picture: AFP/NASA/JPL-Caltech/SSI

No one yet knows whether any planets beyond our solar system have even more moons than Saturn.

VIDEO: The work by the Cassini spacecraft showed us that two of Saturn’s moons have some features that could support life

Is there life on Saturn's moons?

Dr Sheppard is a 42-year-old American astronomer.

At university, he first studied a type of science called physics.

He has discovered dozens of moons around Jupiter, Saturn, Uranus and Neptune.

He has also discovered comets, lots of dwarf planets, centaurs* and other celestial* bodies.

In 2018 he was the lead discoverer of the most distant object in our solar system, dwarf planet 2018 VG18, nicknamed Farout.

Three comets are named after him: Sheppard-Trujillo, Sheppard-Tholen and Trujillo-Sheppard.

The Uranus with moons from space showing all they beauty media_cameraUranus with some of its moons. Astronomer Scott Sheppard has discovered some of the moons around Uranus.


  • astronomer: scientist who studies objects in space such as planets, moons, stars, comets and galaxies
  • diameter: distance across a circle or sphere
  • inventory: a complete list of things
  • remnants: the bits left behind after the rest has gone
  • centaurs: small space objects a bit like comets but similar in size to asteroids that orbit in the outer Solar System mostly between Jupiter and Neptune
  • celestial: up in the sky or space rather than on Earth


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  1. How many moons do we know Saturn and Jupiter each have?
  2. What does an astronomer do?
  3. What is Ganymede and how big is it?
  4. Could there be other moons around Saturn? Why don’t we know about them yet?
  5. Name three types of celestial objects Dr Sheppard has discovered.


1. Name the moons

Imagine there is a competition to name five of the new moons discovered around Saturn. For each name, write an explanation of the name and why it should be chosen as the winner.

Time: allow 25 minutes to complete this activity
Curriculum Links: English, Critical and Creative Thinking

2. Extension
“Scott Sheppard, astronomy superstar!” OR “Saturn, the moon king!”

Design and create a poster that will help younger kids understand the most important and interesting things about Scott Sheppard’s discoveries.

OR design and create a poster that will help younger kids understand the most important and interesting things about Saturn and its moons.

If possible, you may like to do some more research on Dr Sheppard or Saturn to help complete your poster.

Time: allow 30 minutes to complete this activity
Curriculum Links: English, Science, Visual Arts

Moon for sale
Guess what? You just bought a moon. Pack your bags and get ready for takeoff. You only have a few days to get organised.

Use the suitcase template to pack 10 items you could not live without.

What do you take and why?

Use this suitcase template or draw your own on a blank page to help you pack your bags to your new moon! media_cameraUse this suitcase template or draw your own on a blank page to help you pack your bags to your new moon!

HAVE YOUR SAY: If you discovered a new moon of Saturn’s, what would you call it and why?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

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