Illustration of Saturn and its rings. Image: janez volmajer/Shutterstock
How did Saturn’s distinctive ring form? Researchers from Tokyo Institute of Technology are now suggesting that the icy halo was formed from several thousand Pluto-sized objects.
Saturn remains one of the more distinctive planets of our solar system, with its enormous, orbiting halo making it a point of fascination for both astronomers and those within popular culture.
But despite first being noticed by people thousands of years ago, the first observation of the rings – which measure on average only 10 metres in thickness – was made by Galileo in 1610.
Several thousand Pluto-sized objects
Since then, astronomers have been contemplating how the composition of Saturn’s rings came about, as opposed to the ones seen around Neptune and Uranus.
Throwing its hat into the ring with a possible solution is a team from the Tokyo Institute of Technology, who have presented what it thinks is the most likely origin of the rings.
The search for an answer began by analysing data from the Late Heavy Bombardment period 4bn years ago, when our solar system was experiencing great change as the largest planets underwent orbital migration.
During this time, it is believed that within the Kuiper-Edgeworth Belt, there existed several thousand Pluto-sized objects and many of these could have experienced close encounters with Saturn, Uranus and Neptune.
From left: A diagram charting how these Kuiper-Edgeworth objects are captured by the planets and gradually broken down to form the rings. Image: Hyodo/Charnoz/Ohtsuki/Genda 2016/Icarus
Why are Uranus and Neptune different?
In Saturn’s case, its planetary ring was formed as these enormous objects came within close proximity of the gas giant and collided with one another.
The resulting fragments of only 0.1-10pc of the original mass of the average object – of around 7km in size – were then captured in the planet’s orbit.
This newly developed model would also offer an answer as to what the compositional differences are between Saturn, Uranus and Neptune.
In the case of Saturn’s neighbours, the supercomputer-calculated models for both Uranus and Neptune showed that these planets have a higher density than Saturn, resulting in them having far greater tidal forces.
Comprised of a rocky core and icy mantle, the objects would be absorbed into the orbit of Uranus and Neptune, colliding with one another to form a rocky ring.
However, the weaker tidal forces of Saturn meant that the debris found in the ring was 99.9pc pure water ice.
Implications for exoplant hunt
“These findings illustrate that the rings of giant planets are natural by-products of the formation process of the planets in our solar system,” said the Tokyo Institute of Technology.
“This implies that giant planets discovered around other stars likely have rings formed by a similar process.”
The team’s research – now published in the science journal Icarus – would add to the suggestion that outer exoplanets on the edge of star systems would also display a similar ring formation.
In other Saturn news, NASA today (15 November) revealed a stunning photograph of the planet’s northern hexagonal polar vortex taken by the agency’s Cassini spacecraft on 5 September.
The incredible northern hexagonal polar vortex of Saturn. Image: NASA/JPL-Caltech/Space Science Institute
