Saturn
Saturn is a gas giant with rings and the lowest density in the Solar System.
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Saturn sits sixth from the Sun and is the Solar System’s second-largest planet, trailing only Jupiter. It’s a gas giant with an average radius roughly nine times Earth’s, yet it’s the only planet less dense than water—about 30% less. Despite being almost as big as Jupiter, Saturn has less than a third of its mass, though it still outweighs Earth by over 95 times. It orbits the Sun at 9.59 AU (1,434 million km), taking 29.45 years to complete one lap.
Inside, Saturn likely has a rocky core, then a deep layer of metallic hydrogen, followed by liquid hydrogen and helium, and finally an outer gas layer. Its pale yellow color comes from ammonia crystals in the upper atmosphere. An electrical current in the metallic hydrogen layer generates a magnetic field weaker than Earth’s but with a magnetic moment 580 times greater due to Saturn’s size; this field is about one-twentieth as strong as Jupiter’s. The outer atmosphere is usually bland and low-contrast, though long-lived features do appear, and wind speeds can hit 1,800 kilometers per hour (1,100 miles per hour).
Saturn’s famous ring system is bright and extensive, made mostly of ice particles with some rocky debris and dust. At least 293 moons orbit the planet, with 63 officially named—not counting hundreds of moonlets within the rings. Its largest moon, Titan, is the Solar System’s second-largest moon; it’s bigger than Mercury (though less massive) and is the only moon with a substantial atmosphere.
The planet is named after the Roman god of wealth and agriculture, father of Jupiter. Its astronomical symbol began as a Greek kappa-rho ligature with a horizontal stroke, abbreviating Κρονος (Cronus), the Greek name for the planet. Over time it evolved into a lower-case Greek eta, and in the 16th century a cross was added to Christianize the pagan symbol. The Romans named Saturday—Sāturni diēs, “Saturn’s Day”—after the planet.
Saturn is a gas giant made mostly of hydrogen and helium, lacking a definite surface. It has a “diffuse core” that extends 60% of the way to the surface, composed of a gradient of rock and ice toward the center.
Its average density is just 0.69 g/cm³ because of its atmosphere. Jupiter’s mass is 318 times Earth’s; Saturn’s is 95 times Earth’s. Together, Jupiter and Saturn hold 92% of all planetary mass in the Solar System.
Lore & Background
Saturn is named after the Roman god of wealth and agriculture, father of Jupiter. Its astronomical symbol originated from a Greek abbreviation for Cronus, the Greek name for the planet. The Romans named Saturday after Saturn.
Saturn's interior is thought to consist of a rocky core surrounded by metallic hydrogen, liquid hydrogen and helium, and an outer gas layer. It has a diffuse core extending 60% of the way to the surface. The planet radiates 2.5 times more energy than it receives from the Sun, possibly due to helium droplets raining inward and releasing heat.
The atmosphere is mostly molecular hydrogen and helium, with trace ammonia, acetylene, ethane, and methane. Upper clouds contain ammonia crystals, giving Saturn a pale yellow hue. Wind speeds can reach 1,800 kilometers per hour. Saturn's magnetic field is weaker than Earth's but has a magnetic moment 580 times greater due to its size.
Reader's Guide
Saturn's significance lies in its unique physical characteristics and its prominent ring system, which is composed mainly of ice particles with some rocky debris and dust. The planet's low density—about 30% less than water—makes it an outlier among the planets. Its interior structure, with a diffuse core and a metallic hydrogen layer generating a magnetic field, provides insights into planetary formation and dynamics.
Saturn's many moons, including Titan—the only moon in the Solar System with a substantial atmosphere—and the geyser activity on Enceladus that may affect Saturn's rotation, highlight its complex system. The planet's rotation rates vary by latitude, and its oblate shape, with an equatorial radius over 10% longer than the polar radius, influences its surface gravity. Saturn, together with Jupiter, holds 92% of the total planetary mass in the Solar System, underscoring its role in the Solar System's structure and evolution.
Frequently Asked Questions
What is Saturn?
Saturn is the sixth planet from the Sun and the second-largest in our Solar System, just behind Jupiter. It's a gas giant best known for its spectacular ring system and for being the only planet whose average density is lower than water.
How big is Saturn compared to Earth?
Saturn's average radius is roughly nine times that of Earth, making it nearly as large as Jupiter. Despite that enormous size, it weighs less than a third of Jupiter's mass, though it still outweighs our planet by more than 95 times.
What is Saturn made of?
Beneath its gaseous outer layers, Saturn is thought to have a rocky core wrapped in a deep shell of metallic hydrogen, then liquid hydrogen and helium, and finally the light outer gases we observe. Its average density works out to just 0.69 grams per cubic centimeter, the lowest of any planet in the Solar System.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Saturn (CC BY-SA 4.0).
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