APOD: Grand Canyon Star Trails (2013 Mar 03)

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APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby APOD Robot » Sun Mar 03, 2013 5:06 am

Image Grand Canyon Star Trails

Explanation: One of the natural wonders of planet Earth, the Grand Canyon in the American southwest stretches across this early evening skyscape. The digitally stacked sequence reveals the canyon's layers of sedimentary rock in bright moonlight. Exposed sedimentary rock layers range in age from about 200 million to 2 billion years old, a window to history on a geological timescale. A recent study has found evidence that the canyon itself may have been carved by erosion as much as 70 million years ago. With the camera fixed to a tripod while Earth rotates, each star above carves a graceful arc through the night sky. The concentric arcs are centered on the north celestial pole, the extension of Earth's rotation axis into space, presently near the bright star Polaris.

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Beyond » Sun Mar 03, 2013 5:23 am

Ah yes. The ubiquitous star trails. But somehow the vista seems a lot Grander from the Grand Canyon. It just gives them extra PAZAZZ :!:
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby MargaritaMc » Sun Mar 03, 2013 11:54 am

Following the links from the Apod led to this interesting post in May 2011 about the Pole Star

viewtopic.php?f=9&t=23672#p148407

There is a graphic showing the precession, which I found useful.

The same thread has a great deal of information about Marvin the Paranoid Android :!:

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby orin stepanek » Sun Mar 03, 2013 12:54 pm

The headless hiker! :mrgreen:
I know; I know; just looks that way! :lol2:
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Indigo_Sunrise » Sun Mar 03, 2013 2:03 pm

Gorgeous image!
The Grand Canyon is an awesome place; and the star trails are pretty impressive too! 8-)

(And in the enlarged image, across on the North Rim, there are lights - maybe from the Grand Canyon Lodge located there..?)

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby saturno2 » Sun Mar 03, 2013 2:10 pm

The sky on the Grand Canyon.
Good image
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby MargaritaMc » Sun Mar 03, 2013 2:20 pm

Some facts that I found interesting, provided from a bit of meandering research into today's Apod.

From http://www.constellationsofwords.com/stars/Polaris.html
Greek navigators of old called Polaris; Kynosoura, which means "the Dog's Tail". The name came into our English language as Cynosure, which means "an object that serves as a focal point of attention and admiration" or "Something that serves to guide".

Which is certainly true of the star trails photograph - even if the Grand Canyon does draw some of our attention away.

A delightful discovery was that at Bill Thayer's indispensable LacusCurtius site there is a section of  Ancient Astronomy and Astrology Resources.
http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/home.html

In this can be found the complete and carefully typed-in text of

Richard Hinckley Allen:
Star Names — Their Lore and Meaning


Here are some quotations:
The Arabs also likened the constellation to a Fish, while with all that nation ... it was Al Faṣ, the Hole in which the earth's axle found its bearing.
...

Phoenice was the early Greek name, borrowed from its constellation, for this "lovely northern light" and the "most practically useful star in the heavens"; but for many centuries it has been Stella Polaris, the Pole-star, or simply Polaris, — Riccioli's Pollaris; this position seeming to be first recognized in literature by Dante when he wrote in the Paradiso:

the mouth imagine of the horn
That in the point beginneth of the axis
Round about which the primal wheel revolves.
pages 450ff


Today is overcast and rainy, so this has kept me amused as I can't get out!

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Ann » Sun Mar 03, 2013 4:46 pm

Beyond wrote:Ah yes. The ubiquitous star trails. But somehow the vista seems a lot Grander from the Grand Canyon. It just gives them extra PAZAZZ :!:


Since I like to identify stars and constellations, I often find star trails frustrating.

But this time I was more successful! The tight grouping of trails at far right is the Alpha Persei Moving Cluster. Below and to the right of it, we have the rest of constellation Perseus, which you can also see here.

Just above the horizon is constellation Auriga. You can see another picture of Auriga here, where the pink emission nebulosity is somewhat enhanced! :D

It's a nice APOD! :D The Grand Canyon is stunning, of course. Not that I've ever been there, but it sure looks stunning in photographs.

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby MargaritaMc » Sun Mar 03, 2013 5:04 pm

Ann wrote:
Beyond wrote:Ah yes. The ubiquitous star trails. But somehow the vista seems a lot Grander from the Grand Canyon. It just gives them extra PAZAZZ :!:


Since I like to identify stars and constellations, I often find star trails frustrating.

But this time I was more successful! The tight grouping of trails at far right is the Alpha Persei Moving Cluster. Below and to the right of it, we have the rest of constellation Perseus, which you can also see here.

Just above the horizon is constellation Auriga. You can see another picture of Auriga here, where the pink emission nebulosity is somewhat enhanced! :D

It's a nice APOD! :D The Grand Canyon is stunning, of course. Not that I've ever been there, but it sure looks stunning in photographs.

Ann


Gosh - what good detective work! I'm still new enough to astronomy not to have seen many star trails, but, even so, I would like to have a "still" picture taken before or after, so that I can identify what stars I am looking at. Not being Sherlock Ann :wink: :lol2:

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby nicodemus » Sun Mar 03, 2013 5:36 pm

That is the North Rim Lodge on the far edge of the canyon with Bright Angel Canyon to the east (right) of it. Hiking and mule ride access to the inner canyon is done the Bright Angel trail on the North Rim.

The Bright Angel Fault runs down Bright Angel Canyon, disrupting some of the thick sedimentary cliff forming units sufficiently that a trail is possible. I don't think any Precambrian sedimentary rocks are visible in this image. The Inner Gorge here is walled by metamorphic and intrusive igneous rocks.

It is tough to see every wonderful place in the contiguous US, but certainly the GC ought to be high on any wanderer's list. I favor the North Rim for its more diverse views starting with Bright Angel Point in front of the Lodge. Another advantage during the height of the tourist season is the crowds are much smaller. I have been at some viewpoints on the South Rim where it was nearly impossible to get to the overlook rail owing to the busloads of tourists.

Once you take in the GC, bear in mind that you are in the Golden Circle of National Parks so consider Zion Canyon including the Fingers section (wow), Bryce Canyon, Arches, Cedar Breaks, and Petrified Forest and the Painted Desert. There are little noted state parks also. I enjoyed Snow Canyon and Coral Pink Sand Dunes to name a couple.

Hope you enjoyed my commercial for some of the most beautiful country around. Be sure to pack lots of fluids though, as the common property of all these locations is dryness.
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby BDanielMayfeild » Sun Mar 03, 2013 6:39 pm

The Grand Canyon is one of my favorite places. Nicodemus, you beat me to the keyboard with your answer to Indigo_Sunrise’s question about the lights on the north rim. In addition to many of the places you mentioned, there’s Canyonlands NP in south central Utah and also Sunset Crater (volcanic) and Meteor Crater to the southeast of the Grand Canyon in Arizona, and all these points of interest surround the magnificent Monument Valley in Northern AZ.

As I love deserts and mountains and canyons, I’ve often daydreamed about what we may someday find on some distant world; a planet with a super continent largely drained by a river system much larger than anything presently on earth. Imagine a world where a river larger than the Amazon has carved through a plateau higher than Tibet. In such a place our planet’s Grand Canyon would be a mere side canyon on a main gorge perhaps ten’s of kilometers deep ...

If you doubt that such a place may exist look again at today’s APOD and try counting the stars in this tiny area of the Milky Way. Now remember that planets vastly outnumber stars ...

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby ta152h0 » Sun Mar 03, 2013 7:02 pm

There was a challenge issued by prof Lewin, in the relatively not so distant past, to photograph the entire rotation star trails. Did that ever happen ?
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby owlice » Sun Mar 03, 2013 7:13 pm

A closed mouth gathers no foot.
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Beyond » Sun Mar 03, 2013 8:28 pm

Geeze owlice, you sure fly fast!
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby owlice » Sun Mar 03, 2013 8:45 pm

And silently, too! :owl:
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby ta152h0 » Sun Mar 03, 2013 8:48 pm

I barely got the chance to get my popcorn and watch the show
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Chris Peterson » Sun Mar 03, 2013 9:31 pm

BDanielMayfeild wrote:As I love deserts and mountains and canyons, I’ve often daydreamed about what we may someday find on some distant world; a planet with a super continent largely drained by a river system much larger than anything presently on earth. Imagine a world where a river larger than the Amazon has carved through a plateau higher than Tibet. In such a place our planet’s Grand Canyon would be a mere side canyon on a main gorge perhaps ten’s of kilometers deep ...

There are natural limits on how high mountains can get, or how deep valleys can be cut. Or more precisely, on how steep the walls of mountains and valleys can get. Consider Mars: a massive mountain in Mons Olympus, an incredible canyon in Valles Marineris. Yet if you were near either, they'd seem far less impressive than many much smaller mountains on Earth, or much shallower valleys. Because in order for these to reach their heights and depths, they also had to spread out. You wouldn't be able to identify Mons Olympus as a mountain if you were at its base, and most of Valles Marineris would seem much less deep than the Grand Canyon.

A planet with geologic structures of great height or depth but similar extent to those on Earth would be a very odd planet indeed- materially nothing like a terrestrial planet, and probably with very low gravity.
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby BDanielMayfield » Mon Mar 04, 2013 2:17 am

Chris Peterson wrote:
BDanielMayfeild wrote:As I love deserts and mountains and canyons, I’ve often daydreamed about what we may someday find on some distant world; a planet with a super continent largely drained by a river system much larger than anything presently on earth. Imagine a world where a river larger than the Amazon has carved through a plateau higher than Tibet. In such a place our planet’s Grand Canyon would be a mere side canyon on a main gorge perhaps ten’s of kilometers deep ...

There are natural limits on how high mountains can get, or how deep valleys can be cut. Or more precisely, on how steep the walls of mountains and valleys can get. Consider Mars: a massive mountain in Mons Olympus, an incredible canyon in Valles Marineris. Yet if you were near either, they'd seem far less impressive than many much smaller mountains on Earth, or much shallower valleys. Because in order for these to reach their heights and depths, they also had to spread out. You wouldn't be able to identify Mons Olympus as a mountain if you were at its base, and most of Valles Marineris would seem much less deep than the Grand Canyon.

A planet with geologic structures of great height or depth but similar extent to those on Earth would be a very odd planet indeed- materially nothing like a terrestrial planet, and probably with very low gravity.

The grander than the Grand Canyon planet I was thinking of wouldn’t have to be all that much different than the earth Chris. As I’m sure you know the earth itself has had super continents several times in the past, so rivers with much larger watersheds than anything we have today could very well have existed even here.

But the canyon riddled planet I was thinking of could be, say 10% larger than the earth and if it had, say a 2% lower average density than earth due to enhanced percentages of silicates and other lighter than iron elements it’s surface gravity wouldn’t be very different than that of earth but the continental crust could be significantly thicker and of wider extent than earth’s percentage of continental to basaltic crusts. Add in an ocean covering around 60% of this hypothetical world and it would have a total surface area 4pi(1.1R(earth))^2 = 618,535,000 km^2, and the 40% land area would then be about 247,414,000 km^2, which is about 65% larger than earth’s present land area.

I don’t think that the existence such a planet is impossible, nor even, given the shear number of planets, is its existence even unlikely. Why couldn’t such a planet have an enormously deep gorge cut through a range of mountains taller that our Himalayas?

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Boomer12k » Mon Mar 04, 2013 3:24 am

Oh, God, now I am dizzy!!!!!! If it wasn't the swirling stars, it was the depths of the Grand Canyon!!!!! :shock:

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Ann » Mon Mar 04, 2013 3:46 am

P. A. G. Scheuer wrote:
The highest mountains on earth, reach ~ 4h1; since isostasy is known to occur in the earth’s crust, this is hardly surprising, but we note that the Tibetan plateau, for example, nowhere rises to heights comparable with the theoretical maximum h2 ≃ 45 km corresponding to its 1000 km horizontal extent.


The article I quoted is full of maths, and I can't say I understand it. Anyway, the author definitely made the point that there is a firm limit to how high mountains can be.

The author wrote about the heights of mountains on neutron stars:

Thus, on a neutron star, we estimate h1 = 0·04 to 0·4 mm


That's not a lot.

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby neufer » Mon Mar 04, 2013 4:10 am

Ann wrote:
The author wrote about the heights of mountains on neutron stars:
Thus, on a neutron star, we estimate h1 = 0·04 to 0·4 mm

That's not a lot.

Yes, but considering that the surface gravity is ~ 1011 times that of the Earth
the energy expended climbing a 40 micron neutron star mountain
is equivalent to climbing a 4,000 km mountain on Earth.
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Beyond » Mon Mar 04, 2013 4:58 am

neufer wrote:
Ann wrote:
The author wrote about the heights of mountains on neutron stars:
Thus, on a neutron star, we estimate h1 = 0·04 to 0·4 mm

That's not a lot.

Yes, but considering that the surface gravity is ~ 1011 times that of the Earth
the energy expended climbing a 40 micron neutron star mountain
is equivalent to climbing a 4,000 km mountain on Earth.

Geeze... you'd need a space suit to climb that high :!: :!:
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Chris Peterson » Mon Mar 04, 2013 5:16 am

BDanielMayfield wrote:The grander than the Grand Canyon planet I was thinking of wouldn’t have to be all that much different than the earth Chris. As I’m sure you know the earth itself has had super continents several times in the past, so rivers with much larger watersheds than anything we have today could very well have existed even here.

I think it would. It isn't a matter of the size of the continent- there is much more involved. First of all, it is a misconception that canyons like the Grand Canyon are created by river erosion. Rivers don't cut gorges without rapid uplift- otherwise, you end up with something more like the Mississippi River- a very wide, very slow river in a very flat valley. But more importantly, there's simply a physical limit to the steepness of valleys and mountains, which is determined by the material strength of rock. You can't have a canyon much deeper than the Grand Canyon unless it becomes broader, or is formed of stepped walls. But the impressiveness of the Grand Canyon isn't just a matter of its depth, but of the ratio of its depth to its width. Just as Valles Marineris is almost certainly less impressive than the Grand Canyon if you were standing on its rim, and just as Mons Olympus is far less impressive than Mt Shasta or Mt Fuji, so too would especially large mountains or deep valleys on another planet be similarly disappointing- or at least, nowhere near as impressive as we might imagine.
Chris

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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby BDanielMayfield » Mon Mar 04, 2013 7:00 am

I was well aware of the need for rapid uplift for the formation of deep canyons Chris. I was also aware of physical principles like isostacy and the differing strengths of various types of rocks. The reason I chose a large continent as a setting was that I was speculating on the possibility of canyon systems in which a river (or rivers) of the size of our mighty Colorado might be mere tributaries. If this notion strains people's imaginations, well then I'll close by reminding y'all of something I believe Albert Einstein once said, "The universe is not only stranger than we imagine, it's stranger than we CAN imagine."
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Re: APOD: Grand Canyon Star Trails (2013 Mar 03)

Postby Chris Peterson » Mon Mar 04, 2013 2:58 pm

BDanielMayfield wrote:I was well aware of the need for rapid uplift for the formation of deep canyons Chris. I was also aware of physical principles like isostacy and the differing strengths of various types of rocks. The reason I chose a large continent as a setting was that I was speculating on the possibility of canyon systems in which a river (or rivers) of the size of our mighty Colorado might be mere tributaries. If this notion strains people's imaginations, well then I'll close by reminding y'all of something I believe Albert Einstein once said, "The universe is not only stranger than we imagine, it's stranger than we CAN imagine."

Please understand that I'm not suggesting that a supercontinent with a large drainage system wouldn't be likely to have canyons much deeper and more massive than the Grand Canyon (Valles Marineris demonstrates that). I'm only suggesting that from the ground I'm not at all certain such canyons would be more impressive than the Grand Canyon.

A mountain river an order of magnitude larger than the Colorado would be very impressive, though!
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