APOD: NGC 7822: Stars and Dust Pillars in... (2017 Nov 19)

[APOD Robot]

NGC 7822: Stars and Dust Pillars in Infrared

Explanation: Young stars themselves are clearing out their nursery in NGC 7822. Within the nebula, bright edges and complex dust sculptures dominate this detailed skyscape taken in infrared light by NASA's Wide Field Infrared Survey Explorer (WISE) satellite. NGC 7822 lies at the edge of a giant molecular cloud toward the northern constellation Cepheus, a glowing star forming region that lies about 3,000 light-years away. The atomic emission of light by the nebula's gas is powered by energetic radiation from the hot stars, whose powerful winds and light also sculpt and erode the denser pillar shapes. Stars could still be forming inside the pillars by gravitational collapse, but as the pillars are eroded away, any forming stars will ultimately be cut off from their reservoir of star stuff. This field spans around 40 light-years at the estimated distance of NGC 7822.

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[Alexander331]

Right to the brightest star on the top right edge of the picture, after clicking on the image, there is an orange structure. What is it ?

[Boomer12k]

Wow... flashback to the sixties, man....psychedelic...trippy....

:---[===] *

[heehaw]

Yes! Yesterday's APOD was serenity while todays is, as Boomer says, psychedelic!

[Ann]

Yes! Yesterday's APOD was serenity while todays is, as Boomer says, psychedelic!

Love that comment.

Ann

[rstevenson]

Right to the brightest star on the top right edge of the picture, after clicking on the image, there is an orange structure. What is it ?

Pretty much everything we see in this picture that isn't a star (or a distant galaxy) is the result of energy streaming out from stars pushing against the gas and dust around them. Most of it looks quite chaotic because there's a lot of stars doing the pushing, but the area you mention looks like a smallish concentration of gas and dust with just a few particularly large and bright stars doing the pushing, so you get a nice little bubble shape. That, in a nutshell, is what the stars are doing: blowing bubbles.

Rob

[Alexander331]

Right to the brightest star on the top right edge of the picture, after clicking on the image, there is an orange structure. What is it ?

Pretty much everything we see in this picture that isn't a star (or a distant galaxy) is the result of energy streaming out from stars pushing against the gas and dust around them. Most of it looks quite chaotic because there's a lot of stars doing the pushing, but the area you mention looks like a smallish concentration of gas and dust with just a few particularly large and bright stars doing the pushing, so you get a nice little bubble shape. That, in a nutshell, is what the stars are doing: blowing bubbles.

Rob

Thanks !

[Fred the Cat]

Fred said, "Didn't you know - Orange is the new black!"

Bojo doesn't agree

[sallyseaver]

NGC 7822: Stars and Dust Pillars in Infrared

Explanation: Young stars themselves are clearing out their nursery in NGC 7822. ... This field spans around 40 light-years at the estimated distance of NGC 7822.

I tried to reach the astrophotographer, Francesco Antonucci, via the link provided in order to request permission to feature this APOD image on my blog at http://massvortex.science, but it was returned. The message said: "Message refused"

Are you able to help me forward my message to Francesco, to get permission?

Ciao Bella Francesco,

Chiedo il permesso di usare la tua immagine [APOD 2017, 19 novembre] di NGC 7822 sul mio sito web. Il mio sito web avrà un blog e il suo scopo è quello di supportare l'introduzione della mia nuova teoria per la formazione stellare e la formazione dei pianeti.

Sito: http://massvortex.science

Cordiali saluti,
Sally Seaver

[sallyseaver]

Right to the brightest star on the top right edge of the picture, after clicking on the image, there is an orange structure. What is it ?

Pretty much everything we see in this picture that isn't a star (or a distant galaxy) is the result of energy streaming out from stars pushing against the gas and dust around them. Most of it looks quite chaotic because there's a lot of stars doing the pushing, but the area you mention looks like a smallish concentration of gas and dust with just a few particularly large and bright stars doing the pushing, so you get a nice little bubble shape. That, in a nutshell, is what the stars are doing: blowing bubbles.

Rob

What I really like about this image is how it shows how a nebula is raw material for forming stars. And you can see where star formation has used up the surrounding nebula gases.

My understanding is that the orange-red gas around the orange crescent shape (that Alexander331 is referring to) is mostly hydrogen gas with some helium gas that is created by the multiple stars that are being born in the region. The hydrogen-helium gas is bumping into a clump of existing nebula gas and pushing it into the crescent shape. The proto-stars themselves are too small to be seen with the resolution of the image.

As a star forms, it actually creates and kicks out hydrogen and helium nuclei and electrons--the beginning of its stellar wind. You can see the mostly hydrogen (red) with some helium (orange) gas as part of star formation in the images below; these are images of proto-stars (called proplyds) from a study that the Hubble Space telescope did of the Orion Nebula. (The black in these images are multi-element gases that absorb the full visible spectrum of light.)

Click to view full size image

[geckzilla]

What I really like about this image is how it shows how a nebula is raw material for forming stars. And you can see where star formation has used up the surrounding nebula gases.

My understanding is that the orange-red gas around the orange crescent shape (that Alexander331 is referring to) is mostly hydrogen gas with some helium gas that is created by the multiple stars that are being born in the region. The hydrogen-helium gas is bumping into a clump of existing nebula gas and pushing it into the crescent shape. The proto-stars themselves are too small to be seen with the resolution of the image.

As a star forms, it actually creates and kicks out hydrogen and helium nuclei and electrons--the beginning of its stellar wind. You can see the mostly hydrogen (red) with some helium (orange) gas as part of star formation in the images below; these are images of proto-stars (called proplyds) from a study that the Hubble Space telescope did of the Orion Nebula. (The black in these images are multi-element gases that absorb the full visible spectrum of light.)

Click to view full size image

Those pictures illustrate artifacts around point sources. WISE resolution really isn't that great, and the stars tend to be all fuzzy partly because of the wavelengths, and I think partly also because of the way the data gets combined... Anyway, some sharpening filters have been applied which create some dark spots and rings, and infrared PSF's tend to form rings of dots.

It is also difficult to analyze the colors in this picture because they are more artistic than anything, but even when they are presented scientifically in the typical WISE color palette, red can sometimes be hydrogen-alpha emission, and other times it can be warm dust. Oftentimes it's both together. Context is important. And I think that saying this color is hydrogen and that color is helium is totally wrong. The bands being presented are wide, and you can see more about them here: http://www.astro.ucla.edu/~wright/WISE/passbands.html

Looking at the graph it's easy to see that all of them will cover multiple emission lines, even if you don't know exactly where the emission lines are. Note also that we are supplied no information about exactly which bands were even used, though I suspect it is mostly a combination of W3 and W4.

[sallyseaver]

What I really like about this image is how it shows how a nebula is raw material for forming stars. And you can see where star formation has used up the surrounding nebula gases.

My understanding is that the orange-red gas around the orange crescent shape (that Alexander331 is referring to) is mostly hydrogen gas with some helium gas that is created by the multiple stars that are being born in the region. The hydrogen-helium gas is bumping into a clump of existing nebula gas and pushing it into the crescent shape. The proto-stars themselves are too small to be seen with the resolution of the image.

As a star forms, it actually creates and kicks out hydrogen and helium nuclei and electrons--the beginning of its stellar wind. You can see the mostly hydrogen (red) with some helium (orange) gas as part of star formation in the images below; these are images of proto-stars (called proplyds) from a study that the Hubble Space telescope did of the Orion Nebula. (The black in these images are multi-element gases that absorb the full visible spectrum of light.)

Click to view full size image

Those pictures illustrate artifacts around point sources. WISE resolution really isn't that great, and the stars tend to be all fuzzy partly because of the wavelengths, and I think partly also because of the way the data gets combined... Anyway, some sharpening filters have been applied which create some dark spots and rings, and infrared PSF's tend to form rings of dots.

It is also difficult to analyze the colors in this picture because they are more artistic than anything, but even when they are presented scientifically in the typical WISE color palette, red can sometimes be hydrogen-alpha emission, and other times it can be warm dust. Oftentimes it's both together. Context is important. And I think that saying this color is hydrogen and that color is helium is totally wrong. The bands being presented are wide, and you can see more about them here: http://www.astro.ucla.edu/~wright/WISE/passbands.html

Looking at the graph it's easy to see that all of them will cover multiple emission lines, even if you don't know exactly where the emission lines are. Note also that we are supplied no information about exactly which bands were even used, though I suspect it is mostly a combination of W3 and W4.

Yes, the APOD picture of NGC 7822 is fairly low resolution. Thank you for the reminder that it is primarily infrared data in the APOD picture. So red would tend to mean higher temperature, or "warm dust," yes? The "artistic" use of the orange-red color (orWISE hydrogen-alpha emission colors) for the gases in the upper right of the large image (after you click on the regular APOD image) seem to match the optical colors associated with the early stages of proplyd [protoplanetary disk, or young star object] development, per the proplyd images I included.

Regarding the proplyd images and the characterization of hydrogen and helium gases, the images are in optical wavelengths.

"Only the NASA/ESA Hubble Space Telescope, with its high resolution and sensitivity, can take such detailed pictures of circumstellar discs at optical wavelengths."

https://www.spacetelescope.org/news/heic0917/

All of the colors and bands for the 2 proplyd images came from the Hubble Space Telescope ACS (Advanced Camera for Surveys) in the optical spectrum.
Colours & filters
Band | Wavelength
Optical, B | 435 nm
Optical, V | 555 nm
Optical, H-alpha | 658 nm
Infrared, Z | 850 nm
Infrared, I | 775 nm

I judged the information from this site regarding colors of dust and gases in telescope images to be usable.
http://www.clarkvision.com/articles/col ... llar.dust/
Do you disagree?

[geckzilla]

You're right, those are proplyds. I glossed over your post and thought you pulled them out of the APOD image since they're so similarly colored and blurry. But the similarity in colors is due to human aesthetic considerations, not because they are of similar composition, even though most everything really is hydrogen and helium anyway. If I understand you correctly, that's the inference you're trying to make.

Looking over Clark's page, he is trying to objectively colorize his images correctly according to the human eye's response to certain wavelength. This is again just an aesthetic consideration. Both the Hubble image and the APOD image have been processed differently from Clark's method because they aren't using the same kind of data. In the APOD image we are seeing light that not only passes straight through the dust but emissions from the dust and gas itself. His analysis is not applicable.

You might be interested to preview images quickly in different wavelengths to get a better understanding. I suggest trying Aladin:
http://aladin.u-strasbg.fr/java/nph-ala ... ownloading

Search for NGC 7822 from the search bar at the top, and the DSS data loads by default. After that you can click the WISE button (under the search bar) and turn on the infrared view to see how we see straight through a lot of the clouds. You can also see how different the application of colors is.