Saturday, March 21, 2009

Patterns in Titan transits & shadow passes!

I don't know why, but I've always been fascinated by patterns. Titan's orbital period is approximately equal to 2 weeks + 2 days - 1 hour. So we have 3 patterns superimposed here:

- You can see the time of day for the events slowly march backwards in approximately one hour increments from 4:52 AM to 3:16 PM.

- You can see the lack of transit transition through "barely" a transit to full transit to perfect ringplane transit to full transit to "barely" transit to no transit.

- You can see the altitude at shadow pass start times decrease, then increase. I'm not sure why Mar 28 has 18*43' and not 21*, but I'm just going by what Starry Night Pro indicated. I tried to eliminate as a source of error how far advanced the shadow was when I stopped the software and read off the numbers. The time is when the whole shadow is first visible. I also made a point of recording the minutes of arc as well. Still the March event is lower in the sky than the April 13 event. I'm stumped. The only thing I can think of is the curvature of Saturn's surface is playing a role here.

This pattern is to be expected as the ecliptic is doing its usual "Summer = Sun high, planets low / Winter = Sun low, planets high" pattern. The April 13 event has the highest altitude we're going to see for Saturn this year.

- There's a 4th pattern that I didn't really allude to very much, except with the "Rings flipped" reference. The shadow of Titan starts off to the left of Titan, and thus trailing behind Titan (which is moving left to right in front of Saturn), then it transitions after passing behind the Sun to the state of having the shadow of Titan leading it. You can see that the Aug 2 event has the transit starting in daylight, but the shadow pass starts at 9:25 PM, after sunset. Thus we start with a "Transit first, shadow after" pattern, then go to "Shadow first, transit after" situation.

I didn't continue into 2010, there probably are more there, but the inexorable "time of day for the events marching backwards" pattern will put the transits in full daylight. Not much for photography...

Titan shadow pass start times:
Mar 28 - 4:52 AM - 18*43' alt - No transit.
Apr 13 - 3:40 AM - 19*1' alt
Apr 29 - 2:45 AM - 18*17' alt
May 15 - 1:43 AM - 17*20' alt
May 31 - 12:46 AM - 16*1' alt
Jun 15 - 11:56 PM - 14*20' alt
Jul 01 - 11:04 PM - 12*38' alt - No transit.
Jul 17 - 10:12 PM - 11*6' alt - Titan barely transits, ends at sundown, 8:13PM.
Aug 02 - 9:24 PM - 8*55' alt - Transit starts during daylight, till 10:47PM (but sets at 10).
Aug 18 - 8:37 PM - 6*38' alt - Nice transit, but is setting & close to the Sun.
Sep 03 - 7:52 PM - 4*1' alt - Lost in Sun. Rings exactly edge on. Titan centered on ring plane.
Sep 19 - 7:08 PM - 1*15' alt - Lost in Sun. Rings flipped. Shadow precedes Titan.
Oct 05 - 6:23 PM - 1*18' below horizon.
Oct 21 - 5:42 PM - 4*42' below horizon. Titan just barely transits at 10:23 PM.
Nov 06 - 5:01 PM - 8*8' below horizon. No transit.
Nov 22 - 4:24 PM - 12*25' below horizon. No transit.
Dec 08 - 3:49 PM - 17*13' below horizon. No transit.
Dec 24 - 3:20 PM - 23*11' below horizon. No transit.
I just love patterns and astronomy is chockablock with them!

Saturday, March 7, 2009

The evolution of roads & asking for directions. Really.

I know it's been a long while between posts and I apologize for that. I initially wanted to keep the Halloween post up there for a while just because I think it's an important idea for amateur astronomers (pros too) to use the one night in the year where there'll be kids out and about ready to look through our telescopes.

Then I just got busy & lazy.

So no more excuses, here's something I came up with on my own a couple years ago while driving down Rt. 29 in my brother's Camaro. It's completely off-topic and not particularly astronomical, but that's how the cookie crumbles sometimes.

I had the girls in the back of the car sleeping (as kids are wont to do) so I had to amuse myself while driving. I was taking the girls to a week-long Girl Scout camp in Ferrum, so it was at least a 2 1/2 hour drive. This was just before I started listening to an iPod and the car's radio didn't work, so I had nothing but my thoughts to keep me company.

I kept my eyes on the road and noticed how I could tell that the road ahead was going to curve to the right even before I could see the road surface because I could see the lack of trees ahead and to the right. It was as if I was driving in a tube of treelessness and I could see the tube ahead even if I couldn't yet see the road itself.

I got to thinking about roads, and how smooth asphalt strips like I was on were a recent invention and mused at what a caveman would think of the road & car. I then wandered mentally into what must surely be a gedanken experiment.

I thought about the caveman era, with small villages of 20 or 30 people every 10 or 20 miles in a seemingly trackless expanse of forest. The men were the hunters and the women would go out gathering in the traditional hunter/gatherer society. It came to me that the women were probably the road (trail) builders of their era. They would journey to the same spot on the creek, the same fruit trees and berry patches and wear down a trail with their feet. The trails must've led outward, branching this way & that to the various destinations, the water, food, sources of raw materials for making cord & rope, clay for pottery, that sort of thing. Later on there would be garden sites near the village, but the trails still went onward to the source of water & raw materials.

I mused how the men would go out hunting and initially would follow one of the many trails the women made until at some point they'd veer off the trail and head into the forest to hunt. Then the men would be on their own, without the familiar landmarks that they had along the trail. Women, using the trail, would use the landmarks, a particular tree or rock outcropping to tell where they were, but the men would have to make a rather large map in their heads to orient themselves. They'd also have to be able to navigate by the Sun & the stars too. I was rather attracted to this explanation due to my astronomical background.

Then it occurred to me that a man who couldn't make such a mental map, or who couldn't otherwise navigate in the forest wouldn't be able to find his way back to the life-sustaining village and would likely become tiger chow. Thus I came to believe that this might be the origin of the male reticence regarding asking for directions while driving his car (as I was doing at that very moment).

A man back then who had to ask directions was a dead man.
And dead men leave no descendants.

I don't want to ask directions because I frakkin' evolved not to ask! I can find my own way with my maps, mental or otherwise, so I don't need to ask anybody for directions. I also don't even want to ask directions, it's almost a point of pride that I can find my own way without help. It's like a puzzle and I want to figure it out for myself. It's purely conjecture but it sure looks like evolution's at work and powerful forces are at play. Better not mess with Mother Nature, ya know!

It's a guy thing.