APOD: Dark River Wide Field (2010 Jul 19)

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APOD: Dark River Wide Field (2010 Jul 19)

Post by APOD Robot » Mon Jul 19, 2010 4:04 am

Image Dark River Wide Field

Explanation: A Dark River of dust seems to run from our Galactic Center, then pool into a starfield containing photogenic sky wonders. Scrolling right will reveal many of these objects including (can you find?) the bright orange star Antares, a blue(-eyed) horsehead nebula, the white globular star cluster M4, the bright blue star system Rho Ophiuchi, the dark brown Pipe nebula, the red Lagoon nebula, the red and blue Trifid nebula, the red Cat's Paw Nebula, and the multicolored but still important center of our Galaxy. This wide view captures in exquisite detail about 50 degrees of the nighttime sky, 100 times the size of the full Moon, covering constellations from the Archer (Sagittarius) through the Snake Holder (Ophiuchus), to the Scorpion (Scorpius). The Dark River itself can be identified as the brown dust lane connected to Antares, and spans about 100 light years. Since the Dark River dust lane lies only about 500 light years away, it only appears as a bridge to the much more distant Galactic Center, that actually lies about 25,000 light years farther away.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Ann » Mon Jul 19, 2010 7:17 am

This is an amazing image. Can you imagine how much work went into producing it? No, I can't either, but if it was easy to do something like this we would surely see many more images like this one. The fact that we don't is testimony to the herculean effort it took to make this image.

It's a little confusing but fun that the picture is "upside down" from a Northerner's perspective. It challenges our "north is up" complacency, because in reality, no direction in space is "up".

All the fantastic nebulosity that is brought out in this picture really challenges our idea of the constellation of Scorpius, too. This is how most of us think about Scorpius, I think:

Image

This image is great, too, and it was even better when I found it on the Internet. This site shrinks many images, which is very good in some cases, I must admit. Still, even in its original size the picture above was not nearly as deep as Rogelio Bernal Andreo's picture. Even when the above image was larger it would have been impossible to pick out the Snake Nebula, for example, while that nebula stands out amazingly clear and sharp in today's APOD. And look at the "claws" of the Scorpion. The "claws" are the curving line of blue stars forming an "arc" some distance from Antares and the Rho Ophiuchi area. In the picture that I posted here there is no nebulosity visible at all in the area around the "claws", but in Rogelio Bernal Andreo's image there are amazing amounts of it.

At bottom left of Rogelio Bernal Andreo's image is "the Blue Horse", a blue reflection nebula surrounding blue star Nu Scorpii. Two patches of blue can be seen at the back of the horse's "head": they are reflection nebulae van den Berg 102 and 103. The blue "eye" of the Blue Horse is staring at another blue star, Beta Scorpii. Some distance above and to the left of Beta Scorpii is somewhat brighter-looking Delta Scorpii, which had an outburst and brightened some years ago. Delta is surrounded by some almost beige-looking nebulosity, which may or may not be quite right (the beige color, I mean). Some distance above Delta is bluer-looking Pi Scorpii, surrounded by a lot of nebulosity. Fantastic! Bet you hadn't seen that nebulosity in very many pictures before!

The Antares and Rho Ophiuchi region looks rather unfamiliar, mostly because it is upside down, and partly because this image brings out nebulosity a little differently than most pictures of this region, and partly because the color of a few of the stars is a little off. Antares, the star sitting in the upper part of the large yellow patch, looks blue-white. The star is really yellow-orange, as in the picture above. To the left of Antares in Rogelio Bernal Andreo's image is the white-looking globular cluster, M4, and to the lower left of Antares is the yellow-white fainter-looking globular cluster NGC 6144. Below Antares is the blue star 22 Scorpii, surrounded by a small blue reflection nebula. The star surrounded by a red emission nebula is Sigma Scorpii. The white-looking patch is, I think, a reflection nebula surrounding star HD 147889. The tiny group of stars in the big blue patch of reflection nebulosity is the multiple star Rho Ophiuchi, but it has become too faint here, I think.

To the right of the picture, you have the well-known Milky Way with the pink patch of the Lagoon Nebula, and the small pink and blue Trifid Nebula below it. If you draw a straight line from Antares to the Lagoon Nebula, you will come across blue-looking star Theta Ophiuchi. Below and very slightly to the right of Theta Ophiuchi you can find the Snake Nebula.

As I said before, this image is the product of a herculean effort. I don't know how many images of the sky have been "stitched" together to produce this image. However, when you stitch so many images together a few mistakes may occur. I have already said that I think that Rho Ophiuchi looks too faint in this image, and maybe the blue reflection neubla surrounding it is too small, too. Also Antares looks too blue. Another star has definitely received the wrong color, too. Can anyone spot which one?

Ann
Last edited by Ann on Mon Jul 19, 2010 8:30 am, edited 1 time in total.
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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by nstahl » Mon Jul 19, 2010 8:17 am


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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Ann » Mon Jul 19, 2010 10:55 am

According to the APOD Robot, we can see the Cat's Paw Nebula in Rogelio Bernal Andreo's image. That is not the case. The red nebula that you can see at the bottom right corner of the non-enlarged image is M17, the Omega Nebula. In the largest-sized image, you can also see M16, the Eagle Nebula.

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Last edited by Ann on Mon Jul 19, 2010 12:30 pm, edited 1 time in total.
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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by mexhunter » Mon Jul 19, 2010 11:24 am

This image of Rogelio is undeniably exquisite.
The mosaic is finely processed.
It has everything, texture, color, depth and one of the most beautiful areas of our galaxy.
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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by orin stepanek » Mon Jul 19, 2010 11:41 am

My eyes not too good; I had to blow the picture up to find the M4; and that with my glasses. :?
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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by biddie67 » Mon Jul 19, 2010 1:12 pm

What an effort to create this magnificent photo!!! But I'm having to print off this thread so that I can go back to the photo and use it to try to find all the stars mentioned above ......

Would it be possible to provide an overlay with all the stars mentioned above labelled? I have to admit that I can't be sure where any of the mentioned stars are .......
Last edited by biddie67 on Mon Jul 19, 2010 3:46 pm, edited 2 times in total.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Axel » Mon Jul 19, 2010 2:23 pm

A 50-degree field like this is indeed amazing. But pardon an ignoramus here - is "the multicolored... center of our Galaxy" the area featuring five very bright stars and magenta, beige, and blue clouds, the equivalent of slighly less than one picture height from the left? And if so, what part of the region is most closely in line with the centre?

Geke

Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Geke » Mon Jul 19, 2010 8:03 pm

I agree with Biddie67: the picture is grand, but the description is largely lost on me as a beginner-stargazer. I can't even be sure I've found that Dark River.
A few weeks ago there was a picture of Mars retrograding, with dates shown when one did a mouse-over. Such a thing would have been great on this image, too.

Thanks for providing such Cosmic pictures!

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by mRRRc » Mon Jul 19, 2010 9:25 pm

I am not so familiar with this region. I tried to make out for myself what every patch, star, and shadow was, using an astronomy program. After 15 minutes, I tried upside down and mirrored. That worked... Robert, you could have saved me time by just saying that in the comments :)

Anyway: a great, great work. Fabulous.
Good luck from the other side of the Atlantic.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Ann » Tue Jul 20, 2010 5:03 am

Geke said:
I agree with Biddie67: the picture is grand, but the description is largely lost on me as a beginner-stargazer. I can't even be sure I've found that Dark River.
I quite agree with you that the description is confusing. Take a look at the picture again. You can see a large multicolored patch of nebulosity: a red patch on the left with a blue star inside, a yellow patch on the right with one white-looking and one blue-looking star inside, a small white patch in the middle, and a blue patch below the white one. This is the Antares and the Rho Ophiuchi region.

You need to look at the yellow patch to find Antares. Antares is the white-looking star in the upper part of the yellow patch. (But there is a large faint yellow-brown patch to the upper right of Antares. Ignore it.)

So which one is the dark river? The Apod robot said that the dark river was connected to Antares. Well, that can't be right, because there is no obvious dark dust lane connected to Antares. But take a look at the blue star at the bottom part of the blue patch. That is 22 Scorpii. There is a moderately long straight patch of dark nebulostiy that is seemingly flowing "toward (or "from") 22 Scorpii. But the dark river doesn't quite reach 22 Scorpii. When it comes close to that star, the river breaks up into a pair of "legs" or maybe a "mouth". The dark river looks a bit like a long sleek fish opening its mouth to swallow 22 Scorpii.

I'm pretty sure that this "fish" is the dark river.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by bystander » Tue Jul 20, 2010 5:31 am

I think the "Dark River" is the dark nebula flowing away to the right from the "blue star in the yellow patch".

See APOD 2008 June 3.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Axel » Tue Jul 20, 2010 1:45 pm

Axel wrote:But pardon an ignoramus here - is "the multicolored... center of our Galaxy" the area featuring five very bright stars and magenta, beige, and blue clouds, the equivalent of slighly less than one picture height from the left? And if so, what part of the region is most closely in line with the centre?
Bump.

Dan Schroeder

Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Dan Schroeder » Tue Jul 20, 2010 2:59 pm

Here's a very similar image that's nicely annotated: http://www.gigagalaxyzoom.org/G.html. It was featured on APOD last September (http://apod.nasa.gov/apod/ap090925.html).

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Ann » Tue Jul 20, 2010 6:52 pm

Axel wrote:
Axel wrote:But pardon an ignoramus here - is "the multicolored... center of our Galaxy" the area featuring five very bright stars and magenta, beige, and blue clouds, the equivalent of slighly less than one picture height from the left? And if so, what part of the region is most closely in line with the centre?
Bump.
No, the part you described is not the center of our galaxy at all. What you described is the Antares and the Rho Ophiuchi region. The part of the image that is closest to the center of our galaxy is in dark dust lane at the top right of the image, close to a blue star. Below it, can you see a prominent elongated curving pink patch with no obvious star inside, sitting on the right side of the image inside this long, dark dust lane? The pink patch is the Lagoon Nebula, and the dark dust lane it is sitting in is actually the dust lane that runs all along the disk of our galaxy. In galaxy NGC 891, its equivalent galaxy-encompassing dust lane looks like this:

Image

NGC 891 is a galaxy that we see edge on, and as you can see, the dust lane runs along the entire length of its disk. And the Lagoon Nebula, to return to today's APOD, is projected on top of the galaxy-spanning dust lane of our own galaxy. You can see that this particular dust lane runs at an oblique angle from the top right of this image to the bottom of it, even further right.

Now look at the very top of the dust lane, where the edge of the image cuts it off, so to speak. That is very close to where the center of our galaxy is located, although hidden behind huge amounts of dust.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by DavidLeodis » Tue Jul 20, 2010 10:28 pm

I agree with the others who have posted that this APOD would be an ideal one to have an annotated version.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Axel » Fri Jul 23, 2010 1:20 pm

Thank you for your detailed reply, Ann.

Yes, I know about dust lanes - I was just disoriented by that marvellous picture. So the actual galactic centre is near that spot in the dust lane, roughly halfway up the height of the image, where a blue star is approximately in line with a pink nebula or gas cloud, below the larger pink arc? ("Below" in the sense of the published picture, not north-south.)

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Ann » Sun Jul 25, 2010 9:57 am

Axel wrote:Thank you for your detailed reply, Ann.

Yes, I know about dust lanes - I was just disoriented by that marvellous picture. So the actual galactic centre is near that spot in the dust lane, roughly halfway up the height of the image, where a blue star is approximately in line with a pink nebula or gas cloud, below the larger pink arc? ("Below" in the sense of the published picture, not north-south.)
No, the galactic center is not "roughly halfway up the height of the image". It is very near the top of the image, inside the thick dark dust lane that runs from the top of the picture to the bottom of it.

Scroll right as far as you can. Look at the dark dust lane. Can you find an obvious blue star inside this dust lane, close to the top of the picture? It should be the topmost blue star that you can see, as long as you remember to scroll right as far as you can. Now you are quite close to the center of our galaxy.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Axel » Sun Jul 25, 2010 1:28 pm

Ann wrote:Scroll right as far as you can. Look at the dark dust lane. Can you find an obvious blue star inside this dust lane, close to the top of the picture? It should be the topmost blue star that you can see, as long as you remember to scroll right as far as you can. Now you are quite close to the center of our galaxy.

Ann
Thanks again! The blue point near the "top" of the dust lane - easily found. But then why does the caption call the galactic centre "multicolored"? Axel

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by Ann » Mon Jul 26, 2010 3:20 pm

Thanks again! The blue point near the "top" of the dust lane - easily found. But then why does the caption call the galactic centre "multicolored"? Axel
You are right, it does say that the galactic center is "multicolored". Why does the caption say that? For no good reason. The caption is wrong.

Although...

Image

This is an infrared image of the galactic center. I guess you could argue that it is multicolored. But we can't see it, because it is hidden by dust. Infrared detectors can peer through the dust, which is why this image could be produced, but our eyes can not.

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Re: APOD: Dark River Wide Field (2010 Jul 19)

Post by DavidLeodis » Mon Jul 26, 2010 5:05 pm

It would be greatly appreciated (at least by me! :) ) if someone could please provide an annotated version of the image.

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