Saturn

Saturn is the sixth planet from the Sun and the most famously beautiful planet in the solar system — universally recognized by its spectacular system of rings. The planet is a gas giant similar in composition to Jupiter, second-largest in mass among the planets, with no solid surface and an atmosphere of hydrogen, helium, and trace gases.

The rings are visible in even a small backyard telescope and provide one of the most dramatic "first views" in amateur astronomy. The ring system spans about 175,000 miles in diameter but is remarkably thin — averaging only 30 feet thick in most places. The rings consist of countless individual ice particles ranging in size from sand grains to small mountains, all orbiting Saturn in nearly perfect alignment with the planet's equator.

The origin of the rings is debated. One theory holds that the rings are remnants of a destroyed moon that came too close to Saturn and was torn apart by tidal forces — perhaps as recently as 10-100 million years ago. Other theories suggest the rings are leftover material from Saturn's original planetary formation 4.5 billion years ago. The ongoing Cassini mission data favored the recent-moon hypothesis, but the question is not definitively settled.

Saturn has 146 confirmed moons (as of 2024), more than any other planet in the solar system. The largest moon, Titan, is larger than Mercury, has a dense nitrogen atmosphere, and hosts liquid methane and ethane lakes and rivers on its surface — the only place in the solar system besides Earth with confirmed stable surface liquids. Titan is one of the most promising places to search for non-Earth-like life chemistry. Smaller moon Enceladus shoots water-vapor geysers from a global subsurface ocean, also of intense astrobiological interest.

Saturn's ring tilt relative to Earth changes over its 29-year orbit. Sometimes the rings are tilted wide open and dramatic; sometimes they are nearly edge-on and almost disappear from view. The next ring-plane crossing (when the rings appear edge-on from Earth) occurs in 2025.

Saturn is named for the Roman god of agriculture and time; the planet's symbol descends from his harvesting sickle.