APOD: Young Stars of NGC 346 (2022 May 12)

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APOD: Young Stars of NGC 346 (2022 May 12)

Post by APOD Robot » Thu May 12, 2022 4:07 am

Image Young Stars of NGC 346

Explanation: The massive stars of NGC 346 are short lived, but very energetic. The star cluster is embedded in the largest star forming region in the Small Magellanic Cloud, some 210,000 light-years distant. Their winds and radiation sweep out an interstellar cavern in the gas and dust cloud about 200 light-years across, triggering star formation and sculpting the region's dense inner edge. Cataloged as N66, the star forming region also appears to contain a large population of infant stars. A mere 3 to 5 million years old and not yet burning hydrogen in their cores, the infant stars are strewn about the embedded star cluster. In this false-color Hubble Space Telescope image, visible and near-infrared light are seen as blue and green, while light from atomic hydrogen emission is red.

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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by Ann » Thu May 12, 2022 5:42 am

APOD 12 May 2022 annotated NGC 346 young star cluster maybe old star cluster.png

NGC 346 is a perfect example of a bright young star cluster containing hot massive stars. Note that the stars are of different sizes (which in this photo is a consequence of pixel bleeding from the brightest stars, making them look bigger), and note that the biggest, brightest stars are bluish.

At left is what looks to me like an old cluster. Note that there are very many stars there, and note that the stars are relatively similar in size (and smallish) and that they are yellowish in color.

Of course, this yellow, star-rich patch doesn't have to be a cluster. Instead, it could simply be the star-rich background of relatively old stars peeking through a gap in the nebulosity surrounding NGC 346. But to me, it looks like a cluster.

Compare the appearance of NGC 346 and the swarm of small yellowish stars to one side of it with the APOD of February 8, 2020, which starkly contrasts the young blue stars of NGC 2264 in Monoceros with the old yellow stars of cluster Trumpler 5:

15 Mon and Trumpler 5 APOD February 8 2020 Bray Falls.png
The young blue stars of NGC 2264 and the old yellow stars of Trumpler 5 (top right).
Photo: Bray Falls.


A perfect example of what I mean by young clusters containing both "big" and "small" stars can be seen in the other great young star cluster of the Small Magellanic Cloud, NGC 602:

NGC 602.png
Big and small stars of young star cluster NGC 602. Photo: Hubble.

NGC 346 really stands out in "the main body" of NGC 346. You can spot it at a glance in the portrait below of the Small Magellanic Cloud, because it is the largest, brightest red blob there. But where is that other bright young cluster in a nebula in the Small Magellanic Cloud, NGC 602? It is actually far outside the main body of the SMC, as it is located on the "wing" of this small galaxy:

Click to play embedded YouTube video.
Zooming into NGC 602.
Credit: NASA, ESA, and G. Bacon and the Hubble Heritage Team (STScI/AURA)

So why does the Small Magellanic Cloud have so few large nebulas and bright young clusters compared with its bigger neighbor, the Large Magellanic Cloud? It is simply because the larger bully of a galaxy is not only stealing gas, the star forming raw material, but stars, too, from its hapless smaller neighbor.

Wikipedia wrote:

The Magellanic Bridge (MBR) is a stream of neutral hydrogen that links the two Magellanic Clouds, with a few known stars inside it. It should not be confused with the Magellanic Stream, which links the Magellanic Clouds to the Milky Way. It was discovered in 1963 by J. V. Hindman et al.

There is a continuous stream of stars throughout the Bridge linking the Large Magellanic Cloud (LMC) with the Small Magellanic Cloud (SMC). This stellar bridge is of greater concentration in the western part. There are two major density clumps, one near the SMC, the other midway between the galaxies, referred to as the OGLE Island.

Note in the Wikipedia stub a fantastic animation of stars actually flowing from the Small Magellanic Cloud (elongated object at upper right) to the Large Magellanic Cloud (large round object at center).

Ann
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by orin stepanek » Thu May 12, 2022 11:40 am

What can I say? :shock: very nice! 8-)
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by MarkBour » Thu May 12, 2022 8:04 pm

Ann wrote: Thu May 12, 2022 5:42 am
Note in the Wikipedia stub a fantastic animation of stars actually flowing from the Small Magellanic Cloud (elongated object at upper right) to the Large Magellanic Cloud (large round object at center).

Ann
Cool! If you had not mentioned it, I'd have missed it. It starts out so slowly.

I wonder if those stars were at one time part of an "arm" and are just rotating into alignment with the LMC, or if they are actually flowing straight towards it, which is how it appears in the 2-D projection that we (and GAIA) can see.
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by AVAO » Thu May 12, 2022 8:22 pm

As I understand the situation, the two clouds are approaching each other or will merge in the future. But why the gas and the star connecting strands occur separated? (blue & white lines)

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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by johnnydeep » Thu May 12, 2022 9:33 pm

AVAO wrote: Thu May 12, 2022 8:22 pm
As I understand the situation, the two clouds are approaching each other or will merge in the future. But why the gas and the star connecting strands occur separated? (blue & white lines)
Where does it say what the blue and white paths represent? I can't seem to find any specific reference to them at https://www.dailymail.co.uk/sciencetech ... louds.html (which is where the picture seems to originate from)

BTW, there looks to be a good - if very technical - discussion of the Bridge in the slides presented here, but I'm too dense and impatient to try to follow it. Perhaps more is explained there:

https://www.slideserve.com/melva/study- ... lated+load
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by Ann » Fri May 13, 2022 4:18 am

AVAO wrote: Thu May 12, 2022 8:22 pm
As I understand the situation, the two clouds are approaching each other or will merge in the future. But why the gas and the star connecting strands occur separated? (blue & white lines)

I first found this picture on a site where the size of the picture was ridiculously large, almost 8 MB. Yikes! And I had already used up my three attachments, so I couldn't add the 8 MB image as an attachment. I quickly left that site and started looking for a smaller version of the picture elsewhere.

Yes, but on the original site there is an explanation as to what the white and blue lines mean (which I missed when I left that site so quickly).

This is the caption:
Caption: The white line gives the approximate (average) track of the stellar bridge and the blue line shows the track of the gaseous bridge. The stars and the gas do not follow the same path.
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by Ann » Fri May 13, 2022 4:38 am

I know that this APOD isn't dedicated to NGC 602, but I have to show you a fantastic picture of "NGC 602 and friends":

NGC 602 and Henize 89 HLRGB Tom Peter AKA Astrovetteman.png
NGC 602 and Henize 89. Photo: Tom Peter AKA Astrovetteman.

Note NGC 602 at top. As you can see, it is part of a larger complex of star formation.

NGC 602 is said to be located on the "wing" of the SMC. I'm pretty sure that the wing is related to the Magellanic Bridge. Most likely the wing, and the NGC 602 complex, is part of the Bridge. Certainly it is located on the side of the SMC that is closest to the LMC.


Click to play embedded YouTube video.
Zooming into NGC 602

Note in the Youtube video to the left of NGC 602 a large oval but somewhat faint nebula. I think it is the same oval (and blue-looking) nebula that is seen to the left (east?) of NGC 602 in Tom Peter's, AKA Astrovetteman's image that I posted above.

Ann
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by johnnydeep » Fri May 13, 2022 2:41 pm

Ann wrote: Fri May 13, 2022 4:18 am
AVAO wrote: Thu May 12, 2022 8:22 pm
As I understand the situation, the two clouds are approaching each other or will merge in the future. But why the gas and the star connecting strands occur separated? (blue & white lines)

I first found this picture on a site where the size of the picture was ridiculously large, almost 8 MB. Yikes! And I had already used up my three attachments, so I couldn't add the 8 MB image as an attachment. I quickly left that site and started looking for a smaller version of the picture elsewhere.

Yes, but on the original site there is an explanation as to what the white and blue lines mean (which I missed when I left that site so quickly).

This is the caption:
Caption: The white line gives the approximate (average) track of the stellar bridge and the blue line shows the track of the gaseous bridge. The stars and the gas do not follow the same path.
Ann
Thanks, but you left out the punch line! Also from that site:
https://people.ast.cam.ac.uk/~vasily/gaia_clouds_bridges/info.html wrote:Caption: The offset between the white and the blue line in the image above this one may be due to ram pressure exerted by the Galactic gaseous corona (shown here in orage/red). This drag (resistance) force acts on both stars and gas, but is more effective for the gas as it covers much larger volume. If the gas and the stars started moving at the same time, one can estimate the amplitude of the force and, therefore, the density of the corona.
Though this still doesn't make me fully understand why the coronal drag results in different paths for the stars versus the gas. Here's a combined image of the two paths overlaid on the galactic gaseous corona (why they didn't show this in the original page I don't know):

magellanic bridge.JPG

[ EDIT: fixed the caption to correctly identify the two lines - thanks, AVAO ]
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Last edited by johnnydeep on Sat May 14, 2022 2:40 pm, edited 1 time in total.
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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by AVAO » Sat May 14, 2022 7:01 am

johnnydeep wrote: Fri May 13, 2022 2:41 pm
Ann wrote: Fri May 13, 2022 4:18 am
AVAO wrote: Thu May 12, 2022 8:22 pm

As I understand the situation, the two clouds are approaching each other or will merge in the future. But why the gas and the star connecting strands occur separated? (blue & white lines)

I first found this picture on a site where the size of the picture was ridiculously large, almost 8 MB. Yikes! And I had already used up my three attachments, so I couldn't add the 8 MB image as an attachment. I quickly left that site and started looking for a smaller version of the picture elsewhere.

Yes, but on the original site there is an explanation as to what the white and blue lines mean (which I missed when I left that site so quickly).

This is the caption:
Caption: The white line gives the approximate (average) track of the stellar bridge and the blue line shows the track of the gaseous bridge. The stars and the gas do not follow the same path.
Ann
Thanks, but you left out the punch line! Also from that site:
https://people.ast.cam.ac.uk/~vasily/gaia_clouds_bridges/info.html wrote:Caption: The offset between the white and the blue line in the image above this one may be due to ram pressure exerted by the Galactic gaseous corona (shown here in orage/red). This drag (resistance) force acts on both stars and gas, but is more effective for the gas as it covers much larger volume. If the gas and the stars started moving at the same time, one can estimate the amplitude of the force and, therefore, the density of the corona.
Though this still doesn't make me fully understand why the coronal drag results in different paths for the stars versus the gas. Here's a combined image of the two paths overlaid on the galactic gaseous corona (why they didn't show this in the original page I don't know):


magellanic bridge.JPG
White line - gaseous bridge; Blue line - stellar bridge; Blue "smoke" - HI gas; Red/Orange "smoke" - Galactic gaseous corona

That's it. Thank you for this additional helpful and clarifying explanations.
But the stellar bridge is white and the gaseous bridge is blue, I think.
Jac

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Re: APOD: Young Stars of NGC 346 (2022 May 12)

Post by johnnydeep » Sat May 14, 2022 2:41 pm

AVAO wrote: Sat May 14, 2022 7:01 am
johnnydeep wrote: Fri May 13, 2022 2:41 pm
Ann wrote: Fri May 13, 2022 4:18 am


I first found this picture on a site where the size of the picture was ridiculously large, almost 8 MB. Yikes! And I had already used up my three attachments, so I couldn't add the 8 MB image as an attachment. I quickly left that site and started looking for a smaller version of the picture elsewhere.

Yes, but on the original site there is an explanation as to what the white and blue lines mean (which I missed when I left that site so quickly).

This is the caption:



Ann
Thanks, but you left out the punch line! Also from that site:
https://people.ast.cam.ac.uk/~vasily/gaia_clouds_bridges/info.html wrote:Caption: The offset between the white and the blue line in the image above this one may be due to ram pressure exerted by the Galactic gaseous corona (shown here in orage/red). This drag (resistance) force acts on both stars and gas, but is more effective for the gas as it covers much larger volume. If the gas and the stars started moving at the same time, one can estimate the amplitude of the force and, therefore, the density of the corona.
Though this still doesn't make me fully understand why the coronal drag results in different paths for the stars versus the gas. Here's a combined image of the two paths overlaid on the galactic gaseous corona (why they didn't show this in the original page I don't know):


magellanic bridge.JPG
White line - gaseous bridge; Blue line - stellar bridge; Blue "smoke" - HI gas; Red/Orange "smoke" - Galactic gaseous corona

That's it. Thank you for this additional helpful and clarifying explanations.
But the stellar bridge is white and the gaseous bridge is blue, I think.
Jac
Thanks, you are correct. And I even checked that very thing several times beforehand! I fixed my original post.
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