APOD: The NGC 6914 Complex (2022 Jul 07)

APOD Robot · Post by **APOD Robot** » Thu Jul 07, 2022 4:05 am

The NGC 6914 Complex

Explanation: A study in contrasts, this colorful skyscape features stars, dust, and glowing gas in the vicinity of NGC 6914. The interstellar complex of nebulae lies some 6,000 light-years away, toward the high-flying northern constellation Cygnus and the plane of our Milky Way Galaxy. Obscuring interstellar dust clouds appear in silhouette while reddish hydrogen emission nebulae, along with the dusty blue reflection nebulae, fill the cosmic canvas. Ultraviolet radiation from the massive, hot, young stars of the extensive Cygnus OB2 association ionize the region's atomic hydrogen gas, producing the characteristic red glow as protons and electrons recombine. Embedded Cygnus OB2 stars also provide the blue starlight strongly reflected by the dust clouds. The over 1 degree wide telescopic field of view spans about 100 light-years at the estimated distance of NGC 6914.

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VictorBorun · Post by **VictorBorun** » Thu Jul 07, 2022 5:53 am

I wonder if the dark patches of cold dust are all in the foreground somewhere nearer then 6000 ly or are they more like a pair of jets from NGC 6914?

Ann · Post by **Ann** » Thu Jul 07, 2022 6:19 am

VictorBorun wrote: ↑Thu Jul 07, 2022 5:53 am I wonder if the dark patches of cold dust are all in the foreground somewhere nearer then 6000 ly or are they more like a pair of jets from NGC 6914?

The dark dust is at the same distance as the blue reflection nebulas and the stars illuminating the nebulas. Dust is a prerequisite for reflection nebulas, as dust is scattering light from stars and spreading their light into larger patches. The mechanism is similar to how light from car lights is being spread out in a fog.

: Click to view full size image

I found a really nice picture of NGC 6914:

Image Caption and Credits: Image of the NGC 6914 nebular complex in Cygnus, from the Documentary Photo Gallery of Calar Alto Observatory (Descubre/CAHA/OAUV/DSA). Vicent Peris (OAUV/DSA/PTeam), Jack Harvey (DSA/SSRO/PTeam), Juan Conejero (DSA/PTeam). Entirely processed with PixInsight 1.6.

The picture can be found here. On this page you can find more information about interstellar dust, reflection nebulas and NGC 6914.

Ann

VictorBorun · Post by **VictorBorun** » Thu Jul 07, 2022 10:22 am

Ann wrote: ↑Thu Jul 07, 2022 6:19 am
VictorBorun wrote: ↑Thu Jul 07, 2022 5:53 am I wonder if the dark patches of cold dust are all in the foreground somewhere nearer then 6000 ly or are they more like a pair of jets from NGC 6914?
The dark dust is at the same distance as the blue reflection nebulas and the stars illuminating the nebulas. Dust is a prerequisite for reflection nebulas, as dust is scattering light from stars and spreading their light into larger patches. The mechanism is similar to how light from car lights is being spread out in a fog.
Click to view full size image

Ann

Can there be two sets of dusty patches: one in the foreground and the other mingling with the stellar cluster?

Here I try to discriminate between the two by fiddling with colors. The proposed foreground one stays black and the proposed middleground one turns bluish black

Eclectic Man · Post by **Eclectic Man** » Thu Jul 07, 2022 11:39 am

The beauty of the universe never fails to amaze me.

orin stepanek · Post by **orin stepanek** » Thu Jul 07, 2022 12:15 pm

Emission and reflection Nebulae working there wonders here!

I
wonder if the black was referred to as

[Obscuring interstellar dust
clouds appear in silhouette?/quote]

Chris Peterson · Post by **Chris Peterson** » Thu Jul 07, 2022 1:46 pm

Ann wrote: ↑Thu Jul 07, 2022 6:19 am
VictorBorun wrote: ↑Thu Jul 07, 2022 5:53 am I wonder if the dark patches of cold dust are all in the foreground somewhere nearer then 6000 ly or are they more like a pair of jets from NGC 6914?
The dark dust is at the same distance as the blue reflection nebulas and the stars illuminating the nebulas. Dust is a prerequisite for reflection nebulas, as dust is scattering light from stars and spreading their light into larger patches. The mechanism is similar to how light from car lights is being spread out in a fog.

To be more precise, there are two mechanisms we need to consider, reflection and scattering. These are different processes (with some overlap). When we see brown dust, we're mainly seeing reflection. The apparent color is largely dependent on the color of the dust (modified slightly by the color of the star, but that can largely be taken as white). When we see blue, we're seeing the product of scattered light. Because short wavelengths are preferentially scattered by particles the typical size of interstellar dust, we see blue enhanced. And that also means that, if the dust isn't too thick, we might see things from behind reddened (because of the loss of that blue light to scattering).

Often, of course, we're seeing a combination of all of these things in dusty areas, leading to a wide range of colors.

johnnydeep · Post by **johnnydeep** » Thu Jul 07, 2022 8:06 pm

Huh? I see discussion going on about an APOD I don't see. What I see is this:

APOD: The NGC 6914 Complex (2022 Jul 07)
The NGC 6914 Complex
Image Credit & Copyright: Giorgio Ferrari
Explanation: With roots in a rotating planet, an old tree is centered in this sequence of 137 exposures each 20 seconds long, recorded one night in northern Sicily. Digital camera and fisheye lens were fixed to a tripod to capture the timelapse scene, so the stars trailed through the region's dark sky. That makes it easy to spot the planet's North Celestial Pole. The extension of Earth's axis of rotation in to space is toward the upper left, at the center of the concentric star trail arcs. The Milky Way is there too. The plane of our galaxy stretches across the wide-field of view from north to east (left to right) creating a broadened luminous band of of diffuse starlight.

DonB312 · Post by **DonB312** » Thu Jul 07, 2022 8:55 pm

johnnydeep wrote: ↑Thu Jul 07, 2022 8:06 pm Huh? I see discussion going on about an APOD I don't see. What I see is this:

Same for me. At around 3:00am CDT my personal website downloaded the image of the nebula being discussed above. But when I went to the actual apod.nasa.gov page it shows an image and description of a tree with a background of circular star trails.

I'll see if I can send an email to RJN to let him know.

Chris Peterson · Post by **Chris Peterson** » Thu Jul 07, 2022 9:23 pm

johnnydeep wrote: ↑Thu Jul 07, 2022 8:06 pm Huh? I see discussion going on about an APOD I don't see. What I see is this:

APOD: The NGC 6914 Complex (2022 Jul 07)
The NGC 6914 Complex
Image Credit & Copyright: Giorgio Ferrari
Explanation: With roots in a rotating planet, an old tree is centered in this sequence of 137 exposures each 20 seconds long, recorded one night in northern Sicily. Digital camera and fisheye lens were fixed to a tripod to capture the timelapse scene, so the stars trailed through the region's dark sky. That makes it easy to spot the planet's North Celestial Pole. The extension of Earth's axis of rotation in to space is toward the upper left, at the center of the concentric star trail arcs. The Milky Way is there too. The plane of our galaxy stretches across the wide-field of view from north to east (left to right) creating a broadened luminous band of of diffuse starlight.

That would appear to be tomorrow's APOD. Don't know why you're seeing it, though. I'm not. The site is working fine for me, both with the link for the current day as well as the permanent link with the date in it. Maybe try clearing your cache and reloading?

johnnydeep · Post by **johnnydeep** » Thu Jul 07, 2022 9:29 pm

Chris Peterson wrote: ↑Thu Jul 07, 2022 9:23 pm
johnnydeep wrote: ↑Thu Jul 07, 2022 8:06 pm Huh? I see discussion going on about an APOD I don't see. What I see is this:

APOD: The NGC 6914 Complex (2022 Jul 07)
The NGC 6914 Complex
Image Credit & Copyright: Giorgio Ferrari
Explanation: With roots in a rotating planet, an old tree is centered in this sequence of 137 exposures each 20 seconds long, recorded one night in northern Sicily. Digital camera and fisheye lens were fixed to a tripod to capture the timelapse scene, so the stars trailed through the region's dark sky. That makes it easy to spot the planet's North Celestial Pole. The extension of Earth's axis of rotation in to space is toward the upper left, at the center of the concentric star trail arcs. The Milky Way is there too. The plane of our galaxy stretches across the wide-field of view from north to east (left to right) creating a broadened luminous band of of diffuse starlight.
That would appear to be tomorrow's APOD. Don't know why you're seeing it, though. I'm not. The site is working fine for me, both with the link for the current day as well as the permanent link with the date in it. Maybe try clearing your cache and reloading?

Alright, it's working correctly now. Refreshing today's APOD page had no effect, but going back one APOD day, refreshing THAT page, then forward again to todays page cleared it up. There's a first time for everything I guess...

Starship Asterisk*

APOD: The NGC 6914 Complex (2022 Jul 07)

APOD: The NGC 6914 Complex (2022 Jul 07)

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Re: APOD: The NGC 6914 Complex (2022 Jul 07)

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Re: APOD: The NGC 6914 Complex (2022 Jul 07)

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