In July 1610, Galileo Galilei, inventor of the first practical telescope, trained his invention on a celestial object known to ancient civilizations and first recorded by the Assyrians in the eighth century B.C.: Saturn, one of six planets (including Earth) then known to exist.
What Galileo saw astounded him. What he thought would be an ordinary planet seemed to him to be three separate objects, or perhaps a single object with handles.
Within the small but burgeoning astronomical community of the time, speculation and debate about these and subsequent observations carried on for decades. It wasn’t until Dutch astronomer Christian Huygens, using a more powerful telescope in 1659, figured out that Saturn is a single planet surrounded by a set of rings. A few years later, Robert Hooke corroborated Huygens’ discovery by observing the shadows that the planet and rings cast on each other.
Despite improvements in telescopes since that time, little was learned about Saturn beyond the occasional discovery of one of its satellites. As recently as the early 1970s, Saturn was thought to have only a dozen or so moons. Several spacecraft visits since the late 70s deepened our understanding of the planet, its moons and its rings—but also generated many more unanswered questions.
Of the many things we have learned about the ringed planet, here are some things you probably didn’t know:
It’s the flattest planet
Okay, none of the planets in our solar system is truly “flat,” despite what the flat-Earthers say. But as planets go, Saturn is flatter than any of them: The distance between its north and south poles is 10 percent shorter than its diameter at the equator. Why? Saturn — one of the “gas giant” planets — spins on its axis so fast (one rotation takes only about 10 Earth hours) that it tends to distribute its gases away from its poles and toward its middle.
It has lightning — serious lightning
Lightning on Earth destroys buildings, fries electronic gear, starts fires and kills people — some 6,000 people per year worldwide. It’s a good thing that there aren’t any of these items on Saturn. In 2005, the orbiting Cassini spacecraft discovered that lighting on Saturn is 1,000 times more powerful than the fiercest Earth lightning.
It has a magnetic personality
All planets have a magnetic field. Earth’s magnetic field is what makes magnetic compasses point north and south. Saturn’s magnetic field is almost 600 times stronger than Earth’s, and its magnetosphere — the volume around the planet that is influenced by its magnetic field — is so large that it includes Saturn’s rings and many of its moons.
The rings are barely there
From a distance, Saturn’s rings appear to be a solid, multicolored sheet. The accuracy of that notion stops at “sheet.” Although the rings are very thin (about 30 feet), they are mostly empty space with enough dust, ice particles and small rocks to reflect sunlight. Bonus fact: The different rings (there are eight in all) orbit at different speeds around the planet.
It’s hot! (Sort of)
It’s super-hot in the interior of Saturn, and although temperatures at the surface are around −178 degrees Celsius, it’s quite a bit warmer than its nearest planetary neighbor, Neptune (−214 °C), and not much colder than Jupiter (−148 °C), which is half as far from the sun as Saturn. Saturn radiates more heat than it receives.
It floats! (Sort of)
Saturn is the only planet in the solar system whose density, on average, is less than that of liquid water — which means, if you could construct a kiddie pool large enough, Saturn would float on the water.
Its moons are interesting, too
Saturn’s 62 confirmed moons (with possibly dozens more moons and moonlets waiting to be discovered) are mostly smallish chunks of rock orbiting the planet. A couple of them have more interesting features, though. Titan, Saturn’s largest moon, has a thick atmosphere—the only moon in the solar system to have one. Enceladus is thought to have a liquid ocean under its ice layerand is known to have geysers that spew water vapor into space.
Galileo’s “handles” turned out to be just one of the many fascinating features of this distant planet. It may be a while before we learn much more about it, however. NASA has no current plans to send another spacecraft there, although such a mission is in the agency’s long-range planning. Until then, scientists will just have to build better telescopes.
Cover image credit: dottedhippo / iStock