Saturn, the fifth planet from the Sun is at opposition tonight: it rises at sunset, transits around midnight, and sets at dawn, providing excellent viewing opportunities for amateur astronomers. When planets are at opposition, they are closer to Earth than they are at any other time of the year. For this planet, that means a better opportunity to see its glorious rings, which were discovered pretty much the way most things in astronomy were discovered: bit by bit. (For an example, see my post about Uranus, which came close to being discovered several times before it finally burst onto the scene, ushered in by an organist from the town of Bath in March, 1781; its rings weren’t discovered until 1977).
You see, even though Saturn had been known to the ancients, it wasn’t until Galileo turned his telescope to this planet that humans had any idea there was something unusual about it. And because the telescopes of the day were a bit refractor-y (pun intended), it wasn’t until several decades later that the ring structure became fully understood, as the 17th-century sketches below illustrate. Galileo’s sketches do show substantial improvement between 1610 and 1616, and Huygen’s sketch from 1655 shows the “correct” interpretation of the rings. The full story is recounted very nicely here, which is also where I got the .gif files.
Saturn is a wonderful target for amateur astronomers; it routinely elicits the sidewalk astronmers’ most coveted reaction: “Wow!” With most telescope views, the reaction is “Oh. Nice.” With Saturn, people routinely check the front end of the telescope to see if we’ve pasted a picture on the end! The ring system is so impressive, and so recognizable, that NASA’s Astronomy Picture of the Day website uses Saturn as its favicon (the little graphic in the address bar):
If you’re interested in observing Saturn for yourself, Sky & Telescope’s Alan M. MacRobert has a very nice observing guide to Saturn on the Sky & Tel website. Easily seen in any backyard telescope, and seen well in larger scopes, Saturn is the target of choice to turn someone on to astronomy.
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