APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Comments and questions about the APOD on the main view screen.
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APOD Robot
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APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by APOD Robot » Mon Feb 23, 2015 5:11 am

Image The Milky Way Over the Arizona Toadstools

Explanation: Which is older -- the rocks you see on the ground or the light you see from the sky? Usually it's the rocks that are older, with their origin sentiments deposited well before light left any of the stars or nebulas you see in the sky. However, if you can see, through a telescope, a distant galaxy far across the universe -- further than Andromeda or spiral galaxy NGC 7331 (inset) -- then you are seeing light even more ancient. Featured here, the central disk of our Milky Way Galaxy arches over Toadstool hoodoos rock formations in northern Arizona, USA. The unusual Toadstool rock caps are relatively hard sandstone that wind has eroded more slowly than the softer sandstone underneath. The green bands are airglow, light emitted by the stimulated air in Earth's atmosphere. On the lower right is a time-lapse camera set up to capture the sky rotating behind the picturesque foreground scene.

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by geckzilla » Mon Feb 23, 2015 5:12 am

Today's APOD is a wonderful blend of geology and astronomy. I hadn't thought about comparing the age of the star light and the age of rocks before.
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ShaileshS

Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by ShaileshS » Mon Feb 23, 2015 5:41 am

Hi, I'm a bit confused by this statement in the explanation - "Usually it’s the rocks that are older, with their origin sentiments deposited well before light left any of the stars or nebulas you see in the sky". I thought the stars are formed before any of the planets and if so, the light emitted by a star is more ancient than the material (e.g. rocks) in planet's core/crust. The rocks are formed mere 120-170M years ago which is less than some distant stars at few hundred/thousand light years. No ? Did I miss something basic ? Thanks in advance to those who care to respond/explain/clarify.

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by drlane » Mon Feb 23, 2015 6:01 am

Well it's really really hard to see objects in the sky that are 100s of millions of light years away. Without a telescope is impossible and it will even take a pretty good one to see galaxies that far out.

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Nitpicker » Mon Feb 23, 2015 6:56 am

ShaileshS wrote:Hi, I'm a bit confused by this statement in the explanation - "Usually it’s the rocks that are older, with their origin sentiments deposited well before light left any of the stars or nebulas you see in the sky". I thought the stars are formed before any of the planets and if so, the light emitted by a star is more ancient than the material (e.g. rocks) in planet's core/crust. The rocks are formed mere 120-170M years ago which is less than some distant stars at few hundred/thousand light years. No ? Did I miss something basic ? Thanks in advance to those who care to respond/explain/clarify.
Well, it is not really about the age of the stars, but the age of the starlight, which correlates to the distance of the stars (distance = age of starlight * speed of light). The Sun is billions of years old, but the sunlight we feel today, left the Sun only a few minutes beforehand.

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by CharlesE » Mon Feb 23, 2015 7:04 am

ShaileshS:

The quote you're referring to compares the actual age of the foreground rocks to the travel time of the light from the stars. While one light year is a distance, it also references a the time in years the light has traveled. You're correct that the stars are much older than the foreground rocks.

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Boomer12k » Mon Feb 23, 2015 7:35 am

Truly awe inspiring....

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Spelling....

Post by HellCat » Mon Feb 23, 2015 8:37 am

Did you really mean "sentiments"?
Or
Sediment?

hoohaw

Re: Spelling....

Post by hoohaw » Mon Feb 23, 2015 10:21 am

HellCat wrote:Did you really mean "sentiments"?
Or
Sediment?
The sediments have made a sentimental journey...

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Re: Spelling....

Post by geckzilla » Mon Feb 23, 2015 10:46 am

hoohaw wrote:
HellCat wrote:Did you really mean "sentiments"?
Or
Sediment?
The sediments have made a sentimental journey...
Hah.

Thanks, HellCat. I emailed Bob about it for you.
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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Ann » Mon Feb 23, 2015 11:39 am

What a great picture! Not only does it look beautiful, but the annotated version is so much fun, too! :D

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Ann » Mon Feb 23, 2015 11:44 am

CharlesE wrote:ShaileshS:

You're correct that the stars are much older than the foreground rocks.
Actually, Vega may be younger than some of the foreground rocks. At the very least, Vega is much younger than the Earth itself.

Ann
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tjjharris

Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by tjjharris » Mon Feb 23, 2015 1:21 pm

The caption includes " older, with their origin sentiments deposited well before ". Did you intend to say "sediments"?

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Re: Spelling....

Post by RJN » Mon Feb 23, 2015 1:56 pm

HellCat wrote:Did you really mean "sentiments"?
Or
Sediment?
Oops! Thanks. Fixed it. - RJN

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by rstevenson » Mon Feb 23, 2015 3:27 pm

Ann wrote:
CharlesE wrote:ShaileshS:
You're correct that the stars are much older than the foreground rocks.
Actually, Vega may be younger than some of the foreground rocks. At the very least, Vega is much younger than the Earth itself.
Current estimates make Vega about 1/10th the age of our Sun, or about 450 million years old. That seems to make it older than any rocks identified in this APOD, though younger than some rocks that can be seen elsewhere on the surface of the Earth.

Rob

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Chris Peterson » Mon Feb 23, 2015 3:47 pm

rstevenson wrote:Current estimates make Vega about 1/10th the age of our Sun, or about 450 million years old. That seems to make it older than any rocks identified in this APOD, though younger than some rocks that can be seen elsewhere on the surface of the Earth.
These are young (Eocene) rocks, so we'll see very few stars indeed that are actually younger. On the other hand, a shot like this made elsewhere, with precambrian granite perhaps, would have nearly all the bright stars (certainly most of the naked eye stars) truly younger than the rock formations, with light travel time an insignificant factor.
Chris

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Alex Conley

Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Alex Conley » Mon Feb 23, 2015 10:34 pm

Why in the world is NGC 7331 given such a large uncertainty in distance? The NED distance, compiled from 37 different distance measurements, is 14.3 +- 2.2 Mpc -- so the light travel time is 46.6 +- 7.2 million years. That's a rather smaller range than 50-500 million years -- and NGC 7331 certainly isn't far enough across to account for that range.

They may mean that NCG 7335 and 7337 are also visible in that inset, and they are much farther away -- but if so, that is rather unclear!

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Chris Peterson » Mon Feb 23, 2015 11:31 pm

Alex Conley wrote:Why in the world is NGC 7331 given such a large uncertainty in distance? The NED distance, compiled from 37 different distance measurements, is 14.3 +- 2.2 Mpc -- so the light travel time is 46.6 +- 7.2 million years. That's a rather smaller range than 50-500 million years -- and NGC 7331 certainly isn't far enough across to account for that range.

They may mean that NCG 7335 and 7337 are also visible in that inset, and they are much farther away -- but if so, that is rather unclear!
I take it to mean that the three identified galaxies lie in that range, which is reasonable: ~50 million ly for NGC 7331 and several hundred million ly for the other two.
Chris

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by drlane » Tue Feb 24, 2015 1:07 pm

That is exactly right. There is a phethora of distant background galaxies that appear to be part of the group but are in fact much much further away.

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by DavidLeodis » Tue Feb 24, 2015 1:43 pm

As it must have been dark to take the image to show the astronomical features I'm confused as to how the rocks and the ground near and also some distance from them are so light coloured that they seem almost to be in daylight?

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Chris Peterson » Tue Feb 24, 2015 2:16 pm

DavidLeodis wrote:As it must have been dark to take the image to show the astronomical features I'm confused as to how the rocks and the ground near and also some distance from them are so light coloured that they seem almost to be in daylight?
It's a composite image constructed from a stack of different exposure times. It's also common in images like this to light the foreground with a flash or some other artificial source if natural lighting is too low.
Chris

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by starsurfer » Tue Feb 24, 2015 2:46 pm

Rob Gendler is credited with 3 inset images but I believe all 4 of them are by him.

Also below are links to closer images:

NGC 7331
North America Nebula
Eagle and Swan Nebula
Lagoon and Trifid Nebula

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by Ann » Thu Feb 18, 2016 3:42 am

It's a joy to see this beautiful image again! Thanks to APOD Robot for providing a link to this image almost a year after it was first posted.
APOD Robot wrote:
The green bands are airglow
There seems to be pink bands as well. What are they?

All in all, this is a wonderful image!

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Re: APOD: The Milky Way Over the Arizona... (2015 Feb 23)

Post by neufer » Thu Feb 18, 2016 5:11 am

Click to play embedded YouTube video.
Ann wrote:

APOD Robot wrote:

The green bands are airglow
There seems to be pink bands as well.

What are they?
Art Neuendorffer