Saturn is known for its brilliant ring system. Saturn's rings are the most extensive of any planetary rings in this solar system, but other planets also have rings, including Jupiter and Neptune, which are both Jovian planets.
Jovian planets are gas planets without solid surfaces. Some larger gas giants form planetary rings around them, while others are too small or do not have enough local matter to pull into a ring system.
So how do these system of rings form and what makes one planet conducive to having rings and another not? Let's explore some planets with rings in the solar system and how they came to be.
Ring systems can form around giant planets that have enough gravitational pull to attract small moons, asteroids and other objects into their orbit. "As a moon is pulled closer to a planet, its tidal forces, meaning its gravitational pull on either side, reaches a point where the moon's gravity can't hold itself together anymore," explains Dr. Vahé Peroomian, head physics and astronomy professor at the University of Southern California. "This is known as the Roche limit, and it causes the moon to be torn apart."
As the orbiting moon breaks apart again and again, it is ground down to water, ice and dust particles traveling along the gravitational orbit like water running down a drain. Ring systems are temporary structures, though, since icy particles melt if they're too close to the sun, and smaller particles of dust are drawn toward the planet, burning up in the atmosphere.
Planetary Rings in the Solar System
All of the gas giants in our outer solar system, including Saturn, Jupiter, Uranus and Neptune, have their own ring systems. These outer solar system planets have large masses to attract ring particles, and they orbit far enough away from the sun for water ice to stay frozen.
Read on to learn how each system of rings differs from planet to planet.
Jupiter's ring system has four primary components: the innermost "halo ring" comprised of dust particles; a thin, faint main ring; and two gossamer rings. Jupiter's rings around the outside of the system are commonly called the Amalthea Ring and the Thebe Ring, named after the moons that provided the necessary material following high-speed impacts.
Jupiter's rings were first discovered in 1979 during Voyager 1's initial flyby and investigated once more by the Galileo spacecraft in the 1990s. Although they are unlikely to disappear in our lifetime, Jupiter's rings are potentially shrinking due to the planet's extreme gravitational pull on these thin ring layers.
The Voyager 2 spacecraft captured the first images of Neptune's rings in 1989 using stellar occultation methods to measure the displacement of ultraviolet light. Through this technique, Voyager 2 was able to discern that Neptune has five main rings (Galle, Le Verrier, Lassell, Arago and Adams) and four prominent ring arcs (Liberté, Egalité, Fraternité and Courage). These smaller rings are formed by faint, thin collections of micrometer-sized dust that is shepherded around the ring system by Neptune's four small moons.
Saturn's rings are the most extensive ring system of all the planets in our solar system, inadvertently making this gas giant one of the most exciting planets to recreate for your fourth-grade science project. Saturn's rings are typically divided into 14 distinct sections, with the D ring being the nearest to the planet and Saturn's E ring and Phoebe ring system being the farthest away.
Saturn is composed primarily of hydrogen and helium, and it is actually the only planet in the solar system with less density than water. This reflective gas structure, framed by its distinctive disk-shaped system, makes it one of the farthest planets you can witness in the night sky with the help of a small telescope. If you hope to catch a glimpse of this celestial wonder, the planet and its rings are visible for most of the year except for January and February, when it's closest to the sun. However, Saturn appears brightest when it reaches opposition in August and September.
Uranus has two sets of rings. Astronomer and scientist James L. Elliot and his team discovered the inner rings March 10, 1977, which consist of nine distinct rings. This discovery is more recent in the history of space exploration due to Uranus' rings being made of larger bodies than its sister planets, Jupiter and Neptune. This lack of dust and smaller particles causes the rings of Uranus to appear thin and slightly opaque from Earth's observatories.
One of the two outer rings is reddish like many other rings in the solar system, while the other outer ring appears blue like Saturn's E ring.
Why Doesn't Earth Have Its Own Ring System?
Although Earth is not a minor planet, it doesn't have the mass of giant planets like Uranus and Neptune. Since the Roche limit is the primary mechanism of ring creation, and this phenomenon occurs at a distance roughly 1.5 to 2.5 times a planet's radius, a moon or asteroid would have to travel within roughly 5,592 miles (9,000 kilometers) of our planet to break apart.
It's evident from our night sky that Earth has the gravity to form moons; however, it is unlikely to have the availability of matter small enough to form its own system of rings.
Exploration of Saturn's Rings
The famous astronomer Galileo Galilei discovered the rings of Saturn in 1610 C.E., and since then, most astronomers have theorized that Saturn's rings likely formed simultaneously with the giant planet roughly 4.5 billion years.
However, the Cassini spacecraft probe was launched to conduct deep-space research in 1997, and it spent over a decade between 2004 and 2017 exploring, recording and transmitting data that shed some light on this distant planet.
The Cassini mission set out to achieve several objectives, including an investigation of the exact composition and structure of the 175,226-mile-wide (282,000-kilometer-wide) ring system and its satellite's surfaces.
The Cassini mission spent several years researching the magnetic effects of Saturn's nearby moons. These objects range in size from small moons like Mimas, which are so small that they cannot maintain a round shape, to gargantuan moons like Titan, which is larger than any dwarf planet in the solar system. Cassini also studied the behavior of Saturn's atmosphere and learned more about time-variability on Saturn's largest moon, Titan.
During its pioneering voyage, Cassini sent back some of the most ground-breaking data that forced scientists to reexamine what we think we know about our solar system and space beyond.
One of Cassini's most hypothesis-shattering insights into the world of Saturn was the relatively younger age of its rings.
"If you went back to the time of the dinosaurs, roughly 100 million years ago, and you were to look up at Saturn, you wouldn't see any rings," Peroomian says. "Saturn's rings are extremely new compared to the age of the solar system."
Now That's Interesting
In February 2023, astronomers from the University of Sheffield published a study in the journal Nature about new ring system the team discovered in our solar system. The rings are around Quaoar, a dwarf planet orbiting beyond Neptune. The rings are too small to see directly; instead the team discovered the ring system by observing an occultation, which means the light from a background star was blocked by Quaoar as it orbited the sun. What makes this ring system especially unique is that it's twice as far out as what scientists previously thought was the maximum limit according to the Roche limit, which is the outer limit of where ring systems were thought to be able to survive.
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