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Saturn is a gas giant composed predominantly of hydrogen and helium. It lacks a definite surface, though it is likely to have a solid core. [36] Saturn's rotation causes it to have the shape of an oblate spheroid; that is, it is flattened at the poles and bulges at its equator.
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Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine-and-a-half times that of Earth. It has only one-eighth the average density of Earth, but is over 95 times more massive. Even though Saturn is nearly the size of Jupiter, Saturn has less than one-third of Jupiter's mass. Saturn orbits the Sun ...
Learn about Saturn, the sixth planet from the Sun and the second-largest in our solar system. Find out about its rings, moons, seasons, structure, atmosphere, and more.
- Overview
- Basic astronomical data
The Italian astronomer Galileo in 1610 was the first to observe Saturn with a telescope. Although he saw a strangeness in Saturn’s appearance, the low resolution of his instrument did not allow him to discern the true nature of the planet’s rings.
How far is Saturn from Earth?
Saturn orbits the Sun at a mean distance of 1,427,000,000 km (887 million miles). Its closest distance to Earth is about 1.2 billion km (746 million miles), and its phase angle—the angle that it makes with the Sun and Earth—never exceeds about 6°. Saturn, seen from the vicinity of Earth, thus always appears nearly fully illuminated.
What feature is Saturn known for?
Saturn is surrounded by a ring system. The entire ring system spans nearly 26,000,000 km (16,000,000 miles) when the faint outer rings are included. When viewed through even a small telescope, the planet encircled by its magnificent rings is arguably the most sublime object in the solar system.
What is Saturn's largest moon?
Saturn orbits the Sun at a mean distance of 1,427,000,000 km (887 million miles). Its closest distance to Earth is about 1.2 billion km (746 million miles), and its phase angle—the angle that it makes with the Sun and Earth—never exceeds about 6°. Saturn seen from the vicinity of Earth thus always appears nearly fully illuminated. Only deep space probes can provide sidelit and backlit views.
Like Jupiter and most of the other planets, Saturn has a regular orbit—that is, its motion around the Sun is prograde (in the same direction that the Sun rotates) and has a small eccentricity (noncircularity) and inclination to the ecliptic, the plane of Earth’s orbit. Unlike Jupiter, however, Saturn’s rotational axis is tilted substantially—by 26.7°—to its orbital plane. The tilt gives Saturn seasons, as on Earth, but each season lasts more than seven years. Another result is that Saturn’s rings, which lie in the plane of its equator, are presented to observers on Earth at opening angles ranging from 0° (edge on) to nearly 30°. The view of Saturn’s rings cycles over a 30-year period. Earth-based observers can see the rings’ sunlit northern side for about 15 years and then, in an analogous view, the sunlit southern side for the next 15 years. In the short intervals when Earth crosses the ring plane, the rings are all but invisible.
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Saturn’s rotation period was very difficult to determine. Cloud motions in its massive upper atmosphere trace out a variety of periods, which are as short as about 10 hours 10 minutes near the equator and increase with some oscillation to about 30 minutes longer at latitudes higher than 40°. Scientists attempted to determine the rotation period of Saturn’s deep interior from that of its magnetic field, which is presumed to be rooted in the planet’s metallic-hydrogen outer core. However, direct measurement of the field’s rotation was difficult because the field is highly symmetrical around the rotational axis. At the time of the Voyager encounters, radio outbursts from Saturn, apparently related to small irregularities in the magnetic field, showed a period of 10 hours 39.4 minutes; this value was taken to be the magnetic field rotation period. Measurements made 25 years later by the Cassini spacecraft indicated that the field was rotating with a period 6–7 minutes longer. It was believed that the solar wind is responsible for some of the difference between these two measurements of the rotational period. Not until Cassini flew inside Saturn’s rings on its final orbits was the rotation period accurately measured. By relating waves observed in the rings to slight variations in Saturn’s gravitational field, the rotation period of the planet was determined to be 10 hours 33 minutes 38 seconds. The time differences between the rotation periods of Saturn’s clouds and of its interior have been used to estimate wind velocities (see below The atmosphere).
Because the four giant planets have no solid surface in their outer layers, by convention the values for the radius and gravity of these planets are calculated at the level at which one bar of atmospheric pressure is exerted. By this measure, Saturn’s equatorial diameter is 120,536 km (74,898 miles). In comparison, its polar diameter is only 108,728 km (67,560 miles), or 10 percent smaller, which makes Saturn the most oblate (flattened at the poles) of all the planets in the solar system. Its oblate shape is apparent even in a small telescope. Even though Saturn rotates slightly slower than Jupiter, it is more oblate because its rotational acceleration cancels a larger fraction of the planet’s gravity at the equator. The equatorial gravity of the planet, 896 cm (29.4 feet) per second per second, is only 74 percent of its polar gravity. Saturn is 95 times as massive as Earth but occupies a volume 766 times greater. Its mean density of 0.69 gram per cubic cm is thus only some 12 percent of Earth’s. Saturn’s equatorial escape velocity—the velocity needed for an object, which includes individual atoms and molecules, to escape the planet’s gravitational attraction at the equator without having to be further accelerated—is nearly 36 km per second (80,000 miles per hour) at the one-bar level, compared with 11.2 km per second (25,000 miles per hour) for Earth. This high value indicates that there has been no significant loss of atmosphere from Saturn since its formation. For additional orbital and physical data, see the table.
Learn about Saturn, the sixth planet from the Sun and the second-largest in our solar system. Find out about its rings, moons, atmosphere, structure, formation, and more.
Mar 17, 2023 · Saturn is the sixth planet from the sun and the second-largest planet in the solar system. It has a whopping 145 moons. It's the farthest planet from Earth that's visible to the unaided eye, but ...
Learn about Saturn, the sixth planet from the Sun and the second largest in the solar system. Find out facts, images, stories, and missions related to Saturn and its rings, moons, and atmosphere.
