Saturn’s rings are disappearing…

Yes, you read it correctly… Saturn’s rings are disappearing… Not in the real sense, but only from our point of view on Earth…

How come?

Read on…

First of all, Saturn’s rotation axis is tilted, just like Earth, but with a slightly bigger angle of 27 degrees (Earth’s tilt is 23.5 deg).  Since the rings of Saturn are around its equatorial plane, the rings are also tilted relative to the Sun/Earth.

changing-aspect-saturn-rings_sm.jpg

Refer to the diagram above, as Saturn moves around the Sun with its tilted rings, there will be times when the rings are tilted maximum to us, and times when we will see the rings edge-on.  Since Saturn’s rings are so thin (about 0.2 to 3 km only!), when they are edge-on to us, it seems that the rings have disappeared when view through small telescopes.

Now, we are approaching the “ring plane crossing” period.  So month after month, Saturn’s rings are getting thinner and thinner, until on Sept 4, 2009, they disappeared.  The last time the rings disappeared happened in 1995.

saturn-2003-2007-ani.gif

This animation shows the changing aspects of Saturn’s rings from 2003 to 2007, taken by our local amateur.  Bear in mind that Saturn’s ring plane is not actually wobbling.  The changing aspects of the rings is caused by the changing direction which we view the rings as both our Earth and Saturn orbit the Sun.  Credit: William Chin (Astrophotography Group of Malaysia)

Ring plane crossing happens every 14-15 years during Saturn’s 29.5-year orbit around the Sun.  Although this may not seems to be good news to us, because we will lose a lot of “ooh” and “aah” and “wow” from our friends, ring plane crossing do has scientific values.

When the rings of Saturn are nearly edge-on to Earth, the glare from the rings is reduced considerably, and faint objects near Saturn are easier to see.  Months before and after the ring plane crossings, unique observations of Saturn, its rings and moons can be made from Earth which are available at no other time.

HST Saturn Rings Crossing

The image shows the 1995 ring plane crossing.  At the bottom image two of Saturn’s icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.  Credit: Hubble Space Telescope


Where is Saturn now?
Saturn is high up in the sky now after dark, in Leo, near to Regulus, the brightest star in Leo. 

First, locate Leo famous asterism, the backward question mark that represents the lion’s front part which ends at Regulus, then move about 3 degrees to the east of Regulus and you will find a bright yellowish “star” that is not in a star chart.  This yellowish bright “star” is Saturn. 

If you have a telescope, even if it’s only a small one, Saturn will not disappoint you.  The rings may be thinner now, but it is still easily visible.

Grab your every chance to see Saturn’s rings before it says bye-bye…

080326-9pm-saturn.jpg

Extra: Science @NASA

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~ by thChieh on March 26, 2008.

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