APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

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APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by APOD Robot » Tue Mar 05, 2024 5:05 am

Image NGC 2170: Angel Nebula Abstract Art

Explanation: Is this a painting or a photograph? In this celestial abstract art composed with a cosmic brush, dusty nebula NGC 2170, also known as the Angel Nebula, shines just above the image center. Reflecting the light of nearby hot stars, NGC 2170 is joined by other bluish reflection nebulae, a red emission region, many dark absorption nebulae, and a backdrop of colorful stars. Like the common household items that abstract painters often choose for their subjects, the clouds of gas, dust, and hot stars featured here are also commonly found in a setting like this one -- a massive, star-forming molecular cloud in the constellation of the Unicorn (Monoceros). The giant molecular cloud, Mon R2, is impressively close, estimated to be only 2,400 light-years or so away. At that distance, this canvas would be over 60 light-years across.

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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by Ann » Tue Mar 05, 2024 7:07 am

I've never taken much - or really any - interest in NGC 2170, but it does look spectacular! Let's compare it with NGC 1333:


NGC 1333 is a typical low-mass site of star formation. The dominant color is blue, which is being scattered off the brightest star, BD+30 549, which is spectral class B8V or B9V. This star is blue and reasonably hot, hotter and more massive than Vega or Sirius. It's probably around three solar masses and around 11,000 or 12,000 K. Hot, but no cigar. This star is completely unable to ionize a red emission nebula, but it can indeed light up a blue reflection nebula.

Note the little red blobs and squiggles in the NGC 1333 picture. They are Herbig-Haro objects, jets from newborn (or even unborn) stars.These jets are indeed red from hydrogen alpha emission, because they are ionized as they slam into the surrounding nebula. But you can see how small they are. Note, too, that the dust seems reasonably "undisturbed".


NGC 2170 is clearly a far more violent site of star formation. It forms stars of quite high mass, compared with the low mass stars of NGC 1333. There are stars in NGC 2170 that are more than 20,000 K and possibly more than ten solar masses. This high mass star formation leads to a lot of turmoil. Just look at that dust that seems to be "exploding" out of the nebula center! And look at all that large-scale red hydrogen alpha, Hα. Where does it come from?

Let's look at two nebulas, one that is "just sufficiently ionized to be red", and one that is "just sufficiently un-ionized to be all blue"! I'm talking about the red Cocoon Nebula and the blue Rho Ophiuchi nebula:


The point I wanted to bring home here is that the dividing line between stars ionizing a nebula and stars merely illuminating a nebula goes between spectral classes B1 and B2. Stars of spectral class B1 and hotter ionize a red emission nebula, but stars of spectral class B2 and cooler will typically just illuminate a reflection nebula.

There are exceptions. Star AE Aurigae, of spectral class O9.5V, is ionizing the Flaming Star Nebula and making it glow red. Yes, but there are also tendrils of blue reflection nebulosity scattered across the face of the red nebula:


The reason why there are blue tendrils in the red Flaming Star emission nebula is because there are filaments rich is dust particles in that nebula. The reason why the overwhelming number of red emission nebulas don't have these tendrils of reflection nebulosity is that the hot stars that ionize the nebulas "cook the dust particles to a smaller size", as astrophotographer David Malin once put it, by destroying their icy mantles. That way the particles become too small to scatter visible light.

And the reason why some of the dust in the Flaming Star Nebula has not been destroyed by AE Aurigae is that the star is a speeding runaway stellar sibling which has just blundered into a cloud of gas and dust that it has ionized and lit up. AE Aurigae is passing by so quickly that it hasn't had time to boil away all the icy mantles of all the dust particles in the Flaming Star Nebula.

Let's return to NGC 2170:


Note the nebular patch at upper left, which is both red and blue. The central star of that patch, HD 42004, is spectral class B1.5V. I guess this star is just barely hot enough to ionize a bit of hydrogen alpha, especially if you take into account all the other relatively violent forces going on in this high mass site of star formation. But HD 42004 is certainly also creating its own reflection nebula, hence the combination of red and blue light.

The hottest star inside the entire NGC 2170 region of star formation appears to be the star inside the brightest patch of nebulosity at upper right, BD+46 3474, which is spectral class B1V. This star is hot enough to ionize a red emission nebula. So why is the bright nebula surrounding it all blue? Well, maybe because the star hasn't had time to boil away all the icy mantles of all the dust particles that seem to form a thick soup around the star?

But look at the large red patch at lower center-left. It is red from hydrogen alpha. What's it doing there? I haven't found another B1-type star here, let alone a star that is even hotter. But maybe the dust has cleared a bit here, letting the red hydrogen light that has been ionized by star BD+46 3474 shine through? Remember that hot stars, and BD+46 3474 is at least reasonably hot, cook away the icy mantles of dust particles and make them smaller. So shouldn't those shrunken dust particles scatter shortwave ultraviolet light rather efficiently, the ionization source of hydrogen alpha?

Also, who knows? There is a dark orange-brown dust patch at upper center. Maybe a really massive and ultraviolet star is forming inside that patch, something more massive and more ultraviolet than BD+46 3474?

James Webb, where are you? We need you to take a look at NGC 2170 to see what is really going on in the dust clouds lurking there!

Ann
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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by Christian G. » Tue Mar 05, 2024 2:35 pm

Geez is this image colourful! Blue, pink, brown, orange, black, purple, red, I think the only one missing is green!
I love it when my morning APOD is from the same area I was observing the night before, yesterday I was all over Monoceros and am definitely going back there tonight! And thank you for your rich post, Color Commentator!

DrJoeS

Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by DrJoeS » Tue Mar 05, 2024 6:55 pm

We're gonna need a bigger printer.

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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by AVAO » Tue Mar 05, 2024 7:48 pm

Ann wrote: Tue Mar 05, 2024 7:07 am I've never taken much - or really any - interest in NGC 2170, but it does look spectacular! Let's compare it with NGC 1333:
[...]

James Webb, where are you? We need you to take a look at NGC 2170 to see what is really going on in the dust clouds lurking there!

Ann
ThanX Ann
Exciting comments!

Well, SPITZER has done quite well...
...Although I find the nebulous environment at HERSCHEL even more impressive :roll:

Jac

SPITZER

HERSCHEL

Click to view full size image 1 or image 2
jac berne (flickr)

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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by johnnydeep » Tue Mar 05, 2024 8:14 pm

Yes, NGC 2170 sure is a looker! And it sure beats the pants off of this gem by Cy Twombly from the "abstract painters" link:

--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."{ʲₒʰₙNYᵈₑᵉₚ}

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Ann
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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by Ann » Tue Mar 05, 2024 8:19 pm

AVAO wrote: Tue Mar 05, 2024 7:48 pm
Ann wrote: Tue Mar 05, 2024 7:07 am I've never taken much - or really any - interest in NGC 2170, but it does look spectacular! Let's compare it with NGC 1333:
[...]

James Webb, where are you? We need you to take a look at NGC 2170 to see what is really going on in the dust clouds lurking there!

Ann
ThanX Ann
Exciting comments!

Well, SPITZER has done quite well...
...Although I find the nebulous environment at HERSCHEL even more impressive :roll:

Jac

SPITZER

HERSCHEL

Click to view full size image 1 or image 2
jac berne (flickr)
Thanks, Jac! :D

It really does look as if there is star formation going on in that in that dusty patch that looks orange in the APOD. Although I must say that this dusty area does not look tremendously bright in the infrared, as it probably should have done if there had been a really massive star forming in there. Or am I simply asking too much?

Let's compare the visual and infrared images of NGC 2170 with a visual and an infrared view of NGC 2264, near the Cone Nebula:


As you can see, the hidden star formation in NGC 2264 is more obvious in the NASA/JPL-Caltech infrared image than the possible dust hidden star formation in NGC 2170 is in the Spitzer and Herschel images. At least I think so.

Ann
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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by AVAO » Tue Mar 05, 2024 8:53 pm

Ann wrote: Tue Mar 05, 2024 8:19 pm
AVAO wrote: Tue Mar 05, 2024 7:48 pm
Ann wrote: Tue Mar 05, 2024 7:07 am I've never taken much - or really any - interest in NGC 2170, but it does look spectacular! Let's compare it with NGC 1333:
[...]

James Webb, where are you? We need you to take a look at NGC 2170 to see what is really going on in the dust clouds lurking there!

Ann
ThanX Ann
Exciting comments!

Well, SPITZER has done quite well...
...Although I find the nebulous environment at HERSCHEL even more impressive :roll:

Jac

SPITZER

HERSCHEL

Click to view full size image 1 or image 2
jac berne (flickr)
Thanks, Jac! :D

It really does look as if there is star formation going on in that in that dusty patch that looks orange in the APOD. Although I must say that this dusty area does not look tremendously bright in the infrared, as it probably should have done if there had been a really massive star forming in there. Or am I simply asking too much?

Let's compare the visual and infrared images of NGC 2170 with a visual and an infrared view of NGC 2264, near the Cone Nebula:


As you can see, the hidden star formation in NGC 2264 is more obvious in the NASA/JPL-Caltech infrared image than the possible dust hidden star formation in NGC 2170 is in the Spitzer and Herschel images. At least I think so.

Ann
Now I do think that massive star formation is taking place there, as I would judge it. But let's wait and see what WEBB tells us in the future.

...by the way, JWST also likes it colorful...
Webb’s Newest Nebula Image Looks Like a Colorful Painting (Jan 26, 2024)
https://petapixel.com/2024/01/26/webbs- ... -painting/

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Ann
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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by Ann » Wed Mar 06, 2024 4:52 am

AVAO wrote: Tue Mar 05, 2024 8:53 pm
Now I do think that massive star formation is taking place there, as I would judge it. But let's wait and see what WEBB tells us in the future.

...by the way, JWST also likes it colorful...
Webb’s Newest Nebula Image Looks Like a Colorful Painting (Jan 26, 2024)
https://petapixel.com/2024/01/26/webbs- ... -painting/

I think you are right about the massive star formation, and I'm probably just too skeptical. I hope you're right, because I'm really fascinated by high-mass star formation! Particularly if it takes place moderately nearby but still at a safe distance, so that nothing will happen to us if the massive stars begin acting up!

And thank you for the link to the page that identified the nebula in the new JWST picture. Because it drives me slightly crazy to be shown a picture of a nebula or a galaxy and be told that this is a nebula, or this is a galaxy, but they won't identify the nebula or the galaxy! It's okay if I recognize the galaxy or the nebula right away, because then I can just poo-poo at the stupid editors that don't know anything - but if I don't....!!!!

And with James Webb, I almost certainly won't recognize what I can see in the picture!

And yeah... there sure is a massive star forming there in N79 in the Large Magellanic Cloud!

Ann
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Re: APOD: NGC 2170: Angel Nebula Abstract Art (2024 Mar 05)

Post by Rauf » Wed Mar 06, 2024 6:51 am

My friend found a cosmic creature in this nebula! I wonder what is it, maybe a bug?
photo_2024-03-04_23-47-40.jpg
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