Skip to main content

Saturn’s rings are jiggling, delightfully enough, due to its wobbly core

Saturn Makes Waves in its Own Rings

Our solar system is full of wonders, like the beauty of Saturn’s rings. But these rings aren’t static — recent research shows that they are gently jiggling.

Astronomers from the California Institute of Technology looked at data about Saturn from the now-defunct Cassini mission which orbited the planet between 2004 and 2017. They investigated the planet’s core, and found that it is not solid, as some previously thought, but is what Caltech describes as “a diffuse soup of ice, rock, and metallic fluids,” which makes for a type of call technically called a fuzzy core.

An illustration of Saturn and its "fuzzy" core.
An illustration of Saturn and its “fuzzy” core. Caltech/R. Hurt (IPAC)

The researchers were able to determine both the composition and the size of the core — which stretches across 60% of the planet’s diameter — by looking at the rings. “We used Saturn’s rings like a giant seismograph to measure oscillations inside the planet,” explained co-author Jim Fuller, assistant professor of theoretical astrophysics at Caltech. “This is the first time we’ve been able to seismically probe the structure of a gas giant planet, and the results were pretty surprising.”

The fuzzy core has a profound effect on the planet. “The fuzzy cores are like a sludge,” explains the lead author of the study, Christopher Mankovich. “The hydrogen and helium gas in the planet gradually mix with more and more ice and rock as you move toward the planet’s center. It’s a bit like parts of Earth’s oceans where the saltiness increases as you get to deeper and deeper levels, creating a stable configuration.”

This sludge oscillates slightly, which makes the whole planet jiggle. In turn, this causes ripples in the rings which the Cassini data showed.

“Saturn is always quaking, but it’s subtle,” says Mankovich. “The planet’s surface moves about a meter every one to two hours like a slowly rippling lake. Like a seismograph, the rings pick up the gravity disturbances, and the ring particles start to wiggle around.”

As well as being a delightful mental image, this finding leads to questions about how gas giants form. The current leading theory of their formation is that they begin with a rocky core. Over time, this core attracts gas through gravity, and these gases eventually form part of the planet. But if Saturn has a fuzzy core, it raises the question of whether gas is a key part of the formation of gas giants earlier than previously thought.

The findings are published in the journal Nature Astronomy.

Editors' Recommendations

Georgina Torbet
Georgina is the Digital Trends space writer, covering human space exploration, planetary science, and cosmology. She…
Long-lost moon could explain how Saturn got its rings
Artistic rendering of the moon Chrysalis disintegrating in Saturn’s intense gravity field. The chunks of icy rock eventually collided and shattered into smaller pieces that became distributed in the thin ring we see today.

Saturn is famed for its beautiful rings, but these rings are something of a puzzle to astronomers. Originally, it was thought that they must have formed around the same time as the planet, over 4 billion years ago. But data from the Cassini spacecraft suggested the rings might be much younger than that, forming less than 100 million years ago. Now, a new study suggests that the rings could have been formed from a long-lost moon, explaining several of Saturn's peculiarities.

Saturn rotates with a tilt of 27 degrees, slightly off the plane at which it orbits the sun, and its rings are tilted too. Recently published research proposes that both of these factors can be explained by a former moon, named Chrysalis, which came close to the planet and was torn apart. Most of the moon was absorbed by the planet, but the rest of it created the stunning rings.

Read more
NASA scrubs the launch of its Space Launch System rocket due to fuel leak
NASA's Space Launch System rocket on the launch pad at NASA's Kennedy Space Center in Florida on Saturday, September 3.

NASA has called off today's planned launch of its new Space Launch System rocket. The launch was to be the start of the Artemis I mission, in which the rocket would carry the uncrewed Orion spacecraft on its mission around the moon. But a liquid hydrogen fuel leak meant the launch had to be scrubbed.

The leak was first observed this morning, Saturday, September 3, when the rocket's tanks were being filled with liquid oxygen and liquid hydrogen which act as fuel for the launch. There was a leak in the liquid hydrogen line which connected to the rocket's core stage, requiring the tanking to be halted.

Read more
How to watch NASA launch its mega moon rocket on Saturday
NASA's SLS rocket on its way to the launchpad.

NASA Live: Official Stream of NASA TV

[UPDATE: NASA scrubbed its first launch attempt on Monday after engineers discovered an issue with one of the rocket's engines shortly before launch. It's now aiming to launch on Saturday, September 3 -- details below]

Read more