Living on the Edge 2

In Living on the Edge, we explored what it means to be living near the rim of the Milky Way galaxy. Short answer: we are gazing out upon the universe with our own galaxy dominating the whole sky -- all 360° of it. This blog entry is an update on the "gazing" part.

Recently we camped at North Twin Lake in Central Oregon. It was a glorious moonless, dark-sky view of the Milky Way over a mirror-smooth lake that reflected stars and even the galactic disk itself.  Here is a photo showing the whole vista as the Milky Way stretched up into the sky.



Of course that tiny rendition -- while it nicely shows the whole view at one glance -- doesn't effectively show how many individual stars are visible on a moonless night in a dark-sky location. Well actually, individual stars that would be visible, if only we had eyes that could see dim pinpoint objects. Granted, we can see many stars with the naked eye, but those are only the relatively bright ones. There are many, many, many more stars that we can't see without help.

Fortunately, we have time-exposure photography (details at the end of the blog entry). Here is a bigger view -- can you count the stars? Let me know when you get to 50 billion; you'll be about halfway there. Notice that the neighboring Andromeda galaxy is visible in the upper-left -- it has a trillion stars to tally.



If we could actually see the Milky Way this well every time we went outside at night -- like we can clearly see the Moon without photographic aids -- I wonder how many songs would have been written about the awesome spectacle?

Fly Me to the Milky Way
There's a Milky Way Out Tonight
Allegheny Milky Way
Milky Way Glow
Milky Way Light Becomes You
By the Light of the Silv'ry Milky Way
How High the Milky Way
Milky Way Light Cocktails
Milky Way River

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As promised, here are some technical details on the photos above.  They are based on a 40-shot composite covering most of the sky, stitched with Microsoft's Image Composite Editor (ICE).  Each frame was taken at f/3.5 and ISO 6400 for 15 seconds -- just long enough to "see" dim stars yet is sufficiently quick to prevent star trails.  The horizontal crop is 94 megapixels; the top of the photo is the zenith, i.e. directly overhead.  In the 70-megapixel vertical crop, the top of the photo is the other end of the sky, i.e. horizon to horizon (minus the trees, which would have shown as upside-down).  Of course, both photos are downsized for the blog post; let me know if you'd like a full-resolution copy.

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We had great fun on that trip to North Twin Lake.  During the day, we watched our grandkids and dog swimming joyfully in the crystal clear water of the volcanic crater. The fun did not end at sunset -- evening started with a beautiful crossing of the super-bright International Space Station overhead.  We even got our campsite neighbors and their kids excited about that event: "There are seven people up there!"  (Actually there were only six; I looked it up later.)  Then more stars came out, with an occasional meteoric remnant from the Perseids.  But for me, the main show that night was seeing the Milky Way spreading out its splendor above the mirror-smooth water.

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Update, January 20, 2016: In Living on the Edge, I said: "Let's tip [the photo] sideways and see how it fits into the galactic context."  Inwardly, I had been a little disappointed about how little of the galaxy's center bulge showed before being interrupted by the pesky horizon.

The North Twin lake photo shows more of the Milky Way than did the earlier Jackson, Wyoming photo.  So, I repeated the exercise of tipping the photo sideways then fitting it into the galactic context. Here is the result, with the Jackson version shown first for comparison. 



That bright spot is actually the galactic core.  So, as we were standing on the shore of North Twin Lake, we were gazing out upon the very center of our galaxy -- along with its reflection in the smooth water.  Cool, huh?

Planetary Conjunctions Aplenty

This year we have been treated to several conjunctions -- times of picturesque planetary sharing in the same section of sky. This photo shows a young Crescent Moon cozying up to Venus, which has been dominating the twilight western sky recently.

Here is a closer view of the pair, where some of the Moon's craters are visible. Also, one can see that the bright dot for Venus is slightly elongated, showing that it, too, is a crescent. (For more information on that phenomenon, see the Pre-Dawn Crescents blog entry.)



Around June 30, Venus and Jupiter had a very close encounter, being only 0.3° apart in the sky. One science writer explained the visual proximity by pointing out that one could hide both of them with a chopstick held at arm's length. (He was right; I tried it.) The house across the street from us provided a nice perspective of how very close the planets were in the sky.



And not just the planets themselves. One of the most rewarding aspects of photographing a close-proximity Jupiter/Venus conjunction is getting a picture showing 6 planetary bodies in the same shot: the two planets plus four of Jupiter's moons:



Here is a Venus-Mars-Uranus-Moon conjunction forming a nice triangle, although it's harder to see Uranus because the planet is rather dim from its vast distance well beyond the orbit of Saturn.



(Funny story: I didn't realize I was including Uranus in this shot until I later examined a sky chart for that day. When I pulled the photo file from my archives, sure enough -- there was Uranus, right where it was supposed to be.)



Have you ever wondered why there are so many planetary conjunctions? After all, there are only 8 major planets, and the sky is very big. How can there be so many visually-close encounters between the planets? The answer is the Ecliptic. When we look up into the night sky, there is an imaginary line called the Ecliptic, made visible below as a dashed line in the Star Walk app's view of the Venus-Mars-Uranus-Moon conjunction photo:



The planets and our Moon always tend to cluster near that line, thus providing plenty of opportunities for close encounters. The ancients could not figure out why this was the case; however they knew that for an eclipse to happen, the moon would have to be crossing the line -- hence the name, "Ecliptic." What is that magical line? It's really nothing more than the orbital plane of the solar system seen edge-wise.


Source page: http://education.nationalgeographic.com/media/orbital-plane/
Image file: http://media.education.nationalgeographic.com/assets/photos/000/285/28546.jpg

We never get to see this oblique viewing angle ourselves, because we are stuck inside that virtual disk. So, as we gaze out at the other planets and the Sun, they are all essentially along a line -- the Ecliptic.

Of course, if every planetary orbit was on exactly the same plane, we would always see them perfectly aligned, like this:




Source page: https://en.wikipedia.org/wiki/Ecliptic
Image file #1: https://en.wikipedia.org/wiki/Ecliptic#/media/File:Ecliptic_plane_side_view.gif
Image file #2: https://en.wikipedia.org/wiki/Ecliptic#/media/File:Ecliptic_plane_top_view.gif

Instead, we see the planets above and below that line at different times since their orbits around the Sun are all inclined slightly differently than ours. Here is a view from a star chart program that shows it well. The green line is Earth's orbit; observe how the other planets' orbits are not quite aligned with ours.


Source page: https://infinitewell.wordpress.com/tag/planetary-alignment/
Image file: https://infinitewell.files.wordpress.com/2008/09/orbital-plane-1.jpg

That allows for lovely patterns like this triangle of Venus, the Crescent Moon, and Mercury from the Tax Day Conjunction blog post:



Here is where the Ecliptic was on that evening:



So, there you have it; planetary movement in a nutshell. (Well, more like "...on a dinner plate.") Pardon me if you already knew everything about the Ecliptic and Solar System's orbital plane. But I often say, "Wow; I learn something new every day." For some of you, perhaps this was your day to have the planets' motions in the sky suddenly make more sense.

If you like these conjunction photos, I posted some more on Flickr (slideshow).

Retractable Landing Gear 2

In my Retractable Landing Gear blog posting, we examined what large birds do with their feet after taking off.  The short answer was that they tuck their feet and legs closely under their bodies, making an aerodynamically smooth surface -- much like an airplane's landing gear folding inward.  But as you can see from the photo above, there are also other uses for those feet during flight.  This osprey at the Outer Banks in North Carolina last May was on his way home bringing a very fresh fish for dinner (still wriggling), gripped securely in his un-retracted talons.

Sometimes a bird's legs are simply too long to tuck completely underneath.  This blue heron near the Ballard Locks in Seattle showed that situation last April:







Of course, landing gear is also useful for, well, landing. At the Crystal Springs Rhododendron Garden a number of years ago, this duck demonstrated a water landing for me by first flaring his wings, then using his webbed feet as water skis:





But my favorite demonstration of avian landing gear in action was this Bald Eagle in the Tetons near Jackson Hole in September:







The eagle's strong, sharp talons turned a dead tree root into a nice perch from which to survey his domain.