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Titan Shadow Transits on Saturn in 2009
Submitted: Monday, 2nd March 2009 by Mike Salway

There’s already been three transits of Titan across Saturn in 2009, and maybe, like me, you’ve been clouded out for most of them. All is not lost, however.

There’s still one more transit of Titan itself in 2009 (a grazing transit, with its shadow, on March 12 at 22:15 AEDST (11:15 UT)), followed by a number of shadow transit events.

With these shadow transits, Titan itself will not cross the disc of Saturn but its shadow will. The shadow transits are actually easier to observe due to the contrast of the dark shadow against the yellowish disc of Saturn.

Below I’ll list details of the Titan shadow transit events for the rest of 2009. Times will be listed in Universal Time (UT/GMT) and Australian Eastern Time (AEDST/AEST). If you live in other parts of the world, calculate your time by adding or subtracting your timezone offset to the Universal Time.

Note: 2nd contact is when the shadow is fully on the planets disc, and 3rd contact is when the shadow first starts to exit the planets disc.

  • 28th March: 2nd contact approx 0845 UT (19:45 AEDST).  Still low in the sky and the sky will still be quite bright. Best to wait until the shadow is at mid-transit, 1015 UT (21:15 AEDST). It will be 15° higher in the sky, and the sky will be much darker. 3rd contact just happens just after 1200 UT (23:00 AEDST) when Saturn is at its highest point.  

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Titan Shadow Transit - March 28 2009
  • April 13: 2nd contact approx 0840 UT (18:40 AEST) when Saturn is still low in the sky and sky still bright. Mid-transit occurs at 1030 UT (20:30 AEST). 3rd contact occurs at about 1230 UT (22:30 AEST).

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Titan Shadow Transit - April 13 2009
  • April 29: 2nd contact at 0740 UT, while the sky is still too bright in Australia. Mid-transit occurs at about 0945 UT (19:45 AEST) and 3rd contact starts at about 1200 UT (22:00 AEST)   

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Titan Shadow Transit - April 29 2009
  • May 15: Already in mid-transit while Saturn is higher in the north, at about 0900 UT (19:00 AEST).  3rd contact starts at about 1130 UT (21:30 AEST). Rhea is also in transit during this one but only extends 0.23 of an arcsecond so will likely be invisible except to large aperture telescopes with sensitive CCD’s.

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Titan Shadow Transit - May 15 2009
  • May 31: Already past mid-transit when the sky gets dark enough to observe. 3rd contact occurs at about 1045 UT (20:45 AEST).

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Titan Shadow Transit - May 31 2009
  • June 16: Saturn heading into the NW sky, 3rd contact at about 1010 UT (20:10 AEST).

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Titan Shadow Transit - June 16 2009
  • The next 3 shadow transits are on July 2, July 18 and August 3 but will be very difficult to observe from Australia as Saturn will be lower in the West when the sky gets dark enough to observe, and the shadow transit will be almost over.

That’s not the last we’ll see of Titan transits or its shadow transits. The tilt of the ring plane is still favourable in 2010, and we’ll see some more transits of Titan - this time across the Southern Hemisphere of Saturn. After 2010, we’ll have to wait another 15 years (until 2025!) before we’ll see transits of Titan across Saturn again.

I’ll list details of the 2010 transit events in a future article, so please keep an eye out for it.

Good luck observing the shadow transits in 2009. I’d love to see your pictures and read your reports of the event.

Article by Mike Salway (iceman). Discuss this article on the IceInSpace Forum.
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