APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

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APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

Post by APOD Robot » Wed Dec 26, 2018 5:06 am

Image NGC 6357: The Lobster Nebula

Explanation: Why is the Lobster Nebula forming some of the most massive stars known? No one is yet sure. Cataloged as NGC 6357, the Lobster Nebula houses the open star cluster Pismis 24 near its center -- a home to unusually bright and massive stars. The overall blue glow near the inner star forming region results from the emission of ionized hydrogen gas. The surrounding nebula, featured here, holds a complex tapestry of gas, dark dust, stars still forming, and newly born stars. The intricate patterns are caused by complex interactions between interstellar winds, radiation pressures, magnetic fields, and gravity. NGC 6357 spans about 400 light years and lies about 8,000 light years away toward the constellation of the Scorpion.

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Re: APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

Post by Boomer12k » Wed Dec 26, 2018 9:41 am

Maybe:
There is a denser area of dust and gas.
More dust falls in...than normal...more gas follows...
So you get more mass falling inward...

Massive stars in the area may perturb more dust and gas to accumulate as they push material and gases away from themselves and into other areas, which might tend to amass more and more material for more massive stars... but it could just be me...

Merry Xmas to all...

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Re: APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

Post by songwriterz » Wed Dec 26, 2018 12:28 pm

Starry, starry night....

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The Shellfish Gift

Post by neufer » Wed Dec 26, 2018 2:19 pm

Click to play embedded YouTube video.
http://chandra.harvard.edu/photo/constellations/scorpius.html wrote:
<<Phaeton was taunted at school for his claim to be the son of a god.

He traveled to the palace of the Sun to ask his father for proof of his divine birth. Apollo acknowledged Phaeton as his son and granted him one wish. Phaeton asked to drive the chariot of the Sun, his father's responsibility of bringing day to the world. Apollo, deeply troubled and regretful, warned his son of the dangers of driving the chariot through a sky littered with monsters. Apollo mentioned the horns of the Bull, the Lion's jaws, the Scorpion's sting and the Crab's claws. Phaeton rashly insisted and, as his father feared, lost his grip on the reins at the sight of the huge Scorpion. With the chariot pulling the burning Sun completely out of control, the Earth became scorched and was saved only by a thunderbolt from Zeus which struck Phaeton dead.>>
Art Neuendorffer

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Re: APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

Post by MarkBour » Thu Dec 27, 2018 6:45 am

The whole structure looks like a massive, watery cave in this image. I don't suppose that one image like this can tell the whole story, but it does make me wonder about the distribution of dust and gas and what its actual 3-D shape might be.
Mark Goldfain

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Re: APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

Post by neufer » Thu Dec 27, 2018 1:36 pm

MarkBour wrote:
Thu Dec 27, 2018 6:45 am

The whole structure looks like a massive, watery cave in this image. I don't suppose that one image like this can tell the whole story, but it does make me wonder about the distribution of dust and gas and what its actual 3-D shape might be.
https://astroanarchy.zenfolio.com/p2725 ... #h3f8f51f1

http://blogs.discovermagazine.com/badas ... CTVKc1OmUk
Art Neuendorffer

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Re: APOD: NGC 6357: The Lobster Nebula (2018 Dec 26)

Post by MarkBour » Fri Dec 28, 2018 5:22 pm

neufer wrote:
Thu Dec 27, 2018 1:36 pm
MarkBour wrote:
Thu Dec 27, 2018 6:45 am

The whole structure looks like a massive, watery cave in this image. I don't suppose that one image like this can tell the whole story, but it does make me wonder about the distribution of dust and gas and what its actual 3-D shape might be.
https://astroanarchy.zenfolio.com/p2725 ... #h3f8f51f1

http://blogs.discovermagazine.com/badas ... CTVKc1OmUk
Wow, thanks, Art. Those are quite fun and lovely! And thanks for the article that helps answer some of my immediate questions. Such a 3-D is basically fabricated based on some assumptions. At a distance of 6000 Ly, we cannot get any meaningful parallax information, right? Apparently the limit of what we can measure accurately thereby is a mere 300 Ly. So, such renderings have to be made with a lot of guessing. Fascinating work, though.

The article you linked mentions use of the colors and knowledge of the ionization energies to place some distances. I remember a discussion here once where a fortuitous light flash (I don't think it was a supernova, just a variable) was able to be used to map the shape of a cavity, as the delay of the flash bouncing off of material allowed distance measurements. Perhaps there are some other methods as well.

I don't know of any scientific value in this case, it is just a natural curiosity to me to wonder about the 3-D shape. In this case, J-P Metsavainio has gone from the science to the 3-D, as opposed to having a 3-D that might help establish any scientific conclusions. His images render the bright turquoise band pretty far forward in the image, whereas I would have thought it was back in the middle of the "cave".

Finally, I also have a bit of a sense of despair about the 3-D shape anyway. Our everyday experience as humans on earth gives a notion of a cave where you would often have a single light source bouncing off the walls and illuminating a real shape to a clearly-defined cavity. And if you were looking at the cave mouth from outside, you might also see the outer boundary of the rock surrounding the cave. Here, we are looking at thin gas and dust that is probably everywhere around this region, and we only see what is illuminated by some means. I always have to check myself and realize that an astronomical image such as this is not the same as the little structures I live with on Earth that may shape my thinking about what the image is. If I understand nebula images at all, yet, they show regions of higher emission or reflection. From this we can make some deductions about the shape of "regions of higher density", but that may sometimes be misleading. And they are so thin that If you were right in the middle of them, you would not even know it, without highly sensitive instruments. Pretty different than a cave wall, in some ways.
Mark Goldfain