December 22, 2014

Astro-Event: A Tax Day Return of Saturn.

Saturn in January 2004. (Photo by Author).

Not looking forward to April 15th and the U.S. deadline to file taxes? It is in trying times like these that one can look to the skies for solace and the return of our solar system’s most resplendent planet to evening skies. Yes, we’re talking about Saturn as it reaches opposition later this weekend on Sunday April 15th at 18:00 Universal Time, or 14:00 Eastern Standard Time. Shining at magnitude +0.8 in the constellation Virgo, Saturn is currently just over seven degrees south of the celestial equator and thus is pretty well placed for observers in either hemisphere.

Saturn is always a welcome highlight to any spring star party. The rings are also currently tipped open about 15° degrees to our line of sight on their way to a maximum opening of 27° degrees in 2017. Fans of this site may remember that Saturn presented its rings edge on to us in 2009, as they will appear again in 2025. Saturn is on a 29.46 year orbit, and this means that Saturnian solstice and equinox pairings happen just shy of 15 years apart.  NASA’s Cassini spacecraft took advantage of the 2009 plane crossing during its extended Equinox Mission to produce some stunning science and images of a ghostly Saturn with rings backlit by the Sun.

So, what should you, the skilled backyard observer, watch for during the 2012 Saturn season? To the naked eye, the rings add about half a magnitude in brightness to Saturn’s visual appearance. Note its close proximity this year to +0.9 magnitude Spica, also known as Alpha Virginis. Saturn may also exhibit an abrupt rise in visual brightness on the days leading up to opposition, owing to our retro-reflective friend, the Seeliger Effect. And on a personal note, I began observing Saturn when it was near this very same spot in the summer of 1983 as a teenager; hence, I’ve been an avowed astronomy nut for one “Saturnian Year!”

How can you tell which is which? By using a simple rule; stars twinkle, planets don’t. This is because planets have a tiny but substantial angular diameter, bigger than the shimmering convection cells overhead. In the case of Saturn, the disk measures 14.5” across, or 20.1” total from ring-tip to ring-tip, about the same visual size of the International Space Station when its directly overhead.

Through a small telescope, the first thing that becomes apparent is the same feature that confounded Galileo; it’s beautiful system of rings, which he drew as cup-like handles. It was up to Christiaan Huygens to confirm the physical structure of the ring system that does not contact the planet itself, as well as discover its largest Moon Titan. Shining at magnitude +8.4, Titan is easily observable and is the final resting place of ESA’s probe which bears Huygens’s name. Huygens landed on Titan in 2005 and this stands as the most distant landing ever completed by mankind. Other moons to watch for are two-faced Iapetus, Ice-geysering Enceladus, and Tethys, Dione, Hyperion, Rhea and Mimas.  Saturn currently has 62 known moons and counting.

This spring into summer is a fine time to show off the wonders of all that is Saturn. Sure, you can see splendid pics of the ring planet online, but a view of Saturn through the telescope never fails to impress, and might just inspire that next Carl Sagan-to-be. Saturn will rise progressively earlier until reaching conjunction with the Sun later this year on October 25th. This also gives us all of the classical naked eye planets excepting Mercury in the early evening skies.

And finally, as if you needed one more reason to point your scope Saturn-ward, the planet will be slipping across into the constellation Libra in 2013 and will be successively lower into the southern hemisphere murk for northern viewers… in fact, the planet won’t see a northern declination again until 2026, all the more reason to make the most of its favorable viewing position now!

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