Galileo saw them in 1610 with his primitive telescope, but he believed that the planet was decked out with a pair of ears. Forty-five years later, with improved optical instruments, Christiaan Huygens finally described them correctly. But what are they really, these famous rings that encircle Saturn and are the source of its renown, even to this day?
In the coming weeks you’ll have the opportunity to discover Saturn and its rings for yourself. Indeed, the planet will be in opposition on May 10, when the distance between it and the Earth will be the shortest of the year. During this favorable period, Saturn is visible from dusk to dawn and reaches its peak in the south in the middle of night. We must take advantage of the two or three hours when the planet is at its highest in the sky to observe it by telescope, because it’s at this point that its image will be more stable and detailed to the eye. So this is the perfect opportunity to dig out that telescope sleeping in the back of your closet!
Throughout the almost 30 years it takes to make a complete orbit around the sun, Saturn shows alternately the south side (the “bottom”) and the north face (the “top”) of its rings. Every 15 years there’s a transition period when the rings are seen on edge: they appear so thin, in amateur instruments they almost completely disappear. This year we don’t have to worry: the rings will appear to us wide open, almost exactly like the picture at the head of this text. But don’t expect to see as much detail as in this photo, captured by the Hubble Space Telescope! Saturn is far away and the laws of optics are unforgiving: to achieve such a result, it takes not only a sizeable instrument with a perfect view, but also a minimum of air turbulence. The small picture below is more representative of Saturn as seen through a telescope of modest size. Quite the difference, right? Nonetheless, we can quite easily distinguish the main components of Saturn’s rings: from the outside to the inside, these are the Rings A and B, separated by the Cassini Division (itself not always easy to detect). Closest to the planet, Ring C is almost completely transparent and more difficult to see through an amateur telescope.
And...an impressive retinue of moons
Speaking of moons, here’s another thing you’ll notice immediately if you point any observation instrument at Saturn: the moon Titan is easily visible beside the planet. This is by far the biggest and brightest of the 62 known moons of Saturn, and it piques the curiosity of scientists. Titan has an extremely dense atmosphere, composed mainly of hydrocarbons: it rains methane, which accumulates on the surface, forming lakes and small rivers. Saturn is a special favorite of many amateur astronomers. Warning: you could become “addicted”... Enjoy the show!