APOD: A Massive Star in NGC 6357 (2010 Nov 21)

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Expand view Topic review: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Sun Nov 18, 2012 9:21 pm

neufer wrote:
DavidLeodis wrote:
I had also wondered about the name Pismis, so it is good to know it is named after Mr Pismis. :)
Is there a Mrs Pismis :?:

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by jo » Mon Jan 17, 2011 12:09 am

i think this is one of the most stunning images so far....or that I've seen so far!! Can anyone tell me if any of these images are avavilable to the general pulic as, say, posters or something similar...I could look at this one for hours...thank you APOD for opening up a whole new universe to me...I have wanted to go "out there" for as long as I can remember...I'm way too old now but at least I can look at these amazing imges and dream....Magic.

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by bystander » Fri Dec 10, 2010 11:07 pm

The Greatest Stars | NASA IOTD | 10 Dec 2010
The small open star cluster Pismis 24 lies in the core of the NGC 6357 nebula in Scorpius, about 8,000 light-years away from Earth. The brightest object in the center of this image is designated Pismis 24-1 and was once thought to weigh as much as 200 to 300 solar masses. This would not only have made it by far the most massive known star in the galaxy, but would have put it considerably above the currently believed upper mass limit of about 150 solar masses for individual stars.

However, Hubble Space Telescope high-resolution images of the star show that it is really two stars orbiting one another that are each estimated to be 100 solar masses.

In addition, spectroscopic observations with ground-based telescopes further reveal that one of the stars is actually a tight binary that is too compact to be resolved even by Hubble. This divides the estimated mass for Pismis 24-1 among the three stars. Although the stars are still among the heaviest known, the mass limit has not been broken due to the multiplicity of the system.

The images of NGC 6357 were taken with Hubble's Wide Field and Planetary Camera 2 in April 2002.

Credit: NASA, ESA, and J. Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain)
Star on a Hubble diet
ESA Hubble Science Release | heic0619 | 11 Dec 2006

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by NoelC » Tue Nov 30, 2010 9:36 pm

Image

-Noel

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by jacobfogg » Tue Nov 23, 2010 11:16 pm

Seriously, some of the pictures that have been posted in these last few days have literally moved me to tears by the grand beauty and majesty of our universe! I know that many won't agree with this statement, but I must say that I am in complete awe of what our God has created!!!

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by Ann » Tue Nov 23, 2010 4:34 am

neufer wrote:
Image
Ann wrote:
Here is another image of Pismis 24 and the star in today's APOD:
Image
The bluish-pink area in the middle of the picture is exactly the part of the
nebula that was strongly turquoise in the Hubble palette image of NGC 6357.
This is the most highly ionized part of the nebula.
http://antwrp.gsfc.nasa.gov/apod/ap081009.html
http://antwrp.gsfc.nasa.gov/apod/ap061220.html
http://antwrp.gsfc.nasa.gov/apod/ap991207.html
Art, space is full of owls. I'm just saying...!

(And thanks for the links!)

Ann

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by Ann » Tue Nov 23, 2010 4:31 am

GaryR wrote:
Ann wrote:
Similarly, in today's APOD, it could be that the colliding stellar winds create the strong emission nebula between the cluster and the star inside a cavity of gas and dust.

Ann
Huh? I thought it was the intense ultraviolet light from the massive stars that causes the emission nebula. Stellar wind just blows the gas away.

Gary
Sometimes colliding stellar winds can indeed make gas and dust "pile up" and make it glow with emission.

This link will take you to APOD from July 26, 2008:

http://apod.nasa.gov/apod/ap080726.html

Here is the same picture, but without the caption:
The gas and dust has become piled up because there are hot massive stars on both sides on it, blowing on it with their furious stellar winds.

As you can see, the picture is in the Hubble palette. There is a lot of blue color in the vicinity of the stars, showing oxygen emission, and testifying to the fact that there are several O stars in here. But the piled-up gas and dust isn't blue, but yellowish. This part of the nebula is completely dominated by hydrogen and sulphur emission.

In traditional RGB photography, the piled up gas and dust between the hot stars in IC 1805 glows very red:
Clearly, though, the highly ionized part of the nebula near Pismis 24 isn't as dusty as the piled-up "walls" between the hot stars in IC 1805.

Actually, oxygen emission is only possible in a very rarified environment, where there is basically no dust and extremely little gas. Could it be that the star sitting in that "cave" in today's APOD is indeed an O star after all, but that there is just too much "gunk" in that cave for the star to be able to ionize the oxygen in its vicinity?

Ann

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by GaryR » Tue Nov 23, 2010 2:18 am

Ann wrote:
Similarly, in today's APOD, it could be that the colliding stellar winds create the strong emission nebula between the cluster and the star inside a cavity of gas and dust.

Ann
Huh? I thought it was the intense ultraviolet light from the massive stars that causes the emission nebula. Stellar wind just blows the gas away.

Gary

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Mon Nov 22, 2010 9:44 pm

Image
Ann wrote:
Here is another image of Pismis 24 and the star in today's APOD:
Image
The bluish-pink area in the middle of the picture is exactly the part of the
nebula that was strongly turquoise in the Hubble palette image of NGC 6357.
This is the most highly ionized part of the nebula.
http://antwrp.gsfc.nasa.gov/apod/ap081009.html
http://antwrp.gsfc.nasa.gov/apod/ap061220.html
http://antwrp.gsfc.nasa.gov/apod/ap991207.html

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by Ann » Mon Nov 22, 2010 6:18 pm

Here is another image of Pismis 24 and the star in today's APOD:
The bluish-pink area in the middle of the picture is exactly the part of the nebula that was strongly turquoise in the Hubble palette image of NGC 6357. This is the most highly ionized part of the nebula.

So the most highly ionized part of the nebula is between hot stars and clusters, not inside clusters or right next to the newborn stars! This reminds me of a star forming region in Sagittarius, NGC 6559:
Isn't this interesting? At upper left you have a bright blue star surrounded by tendrils of dust and a reflection nebula. There is also a large and relatively faint emission nebula centered on it. The star, HD 165921, is alternatively classified as spectral type B6, B0 and O8! Personally I think B0 sounds best, based on the appearance of the nebula. (I fail to see how a B6 star could create an emission nebula at all.)

At the center of the image you have some newborn stars, surrounded by blue reflection nebulosity. I think that the brightest star inside may be HD 166107, classified as a B5 star, which sounds about right based on the appearance of the reflection nebula surrounding it.

But now look at that amazingly bright red "arc" surrounding the B5 star and its siblings like a shell. What causes this strong hydrogen emission? My own guess is that it might be the collision of the stellar wind from the B0 star at top and the young cluster of B-type stars in the bright blue reflection nebula. None of the B-type stars in this picture is able to create a strong emission nebula on its own, but when stellar winds collide hydrogen will glow very red!

Similarly, in today's APOD, it could be that the colliding stellar winds create the strong emission nebula between the cluster and the star inside a cavity of gas and dust.

Ann

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by DavidLeodis » Mon Nov 22, 2010 5:34 pm

I've just found that the APOD image is part of that used for the APOD of 2008 October 26 which was titled 'Massive Stars in Open Cluster Pismis 24'. That APOD is the larger field-of-view image that is brought up through clicking on the APOD. http://antwrp.gsfc.nasa.gov/apod/ap081026.html The explanation to the APOD of 2008 October 26 clearly indicates that the bright star in the APOD of 2010 November 21 is not part of Pismis 24.

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by lewcook » Mon Nov 22, 2010 5:26 pm

Has anyone noticed/commented on/worked on the resemblance of one lobe of the Cat's Paw to the Homunculus around eta Carina? This is best seen in
http://antwrp.gsfc.nasa.gov/apod/ap080304.html
and hinted at in
http://antwrp.gsfc.nasa.gov/apod/ap100421.html

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by DavidLeodis » Mon Nov 22, 2010 5:23 pm

neufer wrote:
DavidLeodis wrote:
I had also wondered about the name Pismis, so it is good to know it is named after Mr Pismis. :)
Is there a Mrs Pismis :?:
Or even a Miss Pismis. :)

Sorry all for that rhyming bit of fun but some of you were bound to at least think it, so I thought it might as well be me that posted it! :oops:

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by Ann » Mon Nov 22, 2010 4:39 pm

I found a Hubble palette image of NGC 6357. Very strange.

Usually I'm quite bored by Hubble palette images, and I will rarely praise them. But they can be useful at times. For example, you can normally expect a nebula to look blue close to an O star if the nebula is shown in the Hubble palette. That is because blue color represents oxygen emission in the Hubble palette, and oxygen emission is usually only present around hot O-type stars. So the blue color of a nebula shown in the Hubble palette tells you that an O star is probably located here.

Well, I found an image of NGC 6357 in the Hubble palette. Guess what? The nebula surrounding the star in today's APOD is not blue!!! Instead the nebula is yellow from a combination of hydrogen and nitrogen. The hydrogen and nitrogen emission combined with the lack of oxygen strongly suggests to me that the star, impressive-looking as it is, is in fact not an O-type star. Most likely it is an early B-type star instead.

The stars in Pismis 24 are also not surrounded by blue light. My guess is that this cluster has blown away the gas and dust that surrounded it.

But an area of strong nebulosity between Pismis 24 and the star in today's APOD is brightly turquoise, suggesting emission of both oxygen, hydrogen and nitrogen. Also, a "cavity" to the right of Pismis 24, to the right of some dark dusty pillars, is strongly blue! Where does this blue light come from????

Something tells me that I may possibly not be allowed to post the image I found, which is why I did my best to describe it. Here, however, is the image, and let's see how long it lasts:
Ann

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Mon Nov 22, 2010 4:02 pm

DavidLeodis wrote:
I had also wondered about the name Pismis, so it is good to know it is named after Mr Pismis. :)
Is there a Mrs Pismis :?:

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by DavidLeodis » Mon Nov 22, 2010 3:19 pm

Thanks Ann for your reply, which is appreciated. My conclusion (probably wrong though!) is that the bright star in the APOD is not part of the Pismis 24 cluster. I had also wondered about the name Pismis, so it is good to know it is named after Mr Pismis. :)

Thanks also neufer, though, as is often the case, I get more confused than ever on reading your replies to posts. They do however make interesting readings. :wink:

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Mon Nov 22, 2010 2:36 pm

DavidLeodis wrote:
I am a bit confused (as usual :) ). Is the very bright star in the APOD part of Pismis 24 or not :?:. Clicking on the APOD brings up a larger field-of-view image that is also reproduced in an earlier post by Ann in which it states it "is another image of NGC 6357, showing more of the cluster Pismis 24". The "showing more" would seem therefore to imply that the bright star in the APOD is part of Pismis 24.
I am assuming that the 8,000 light year distant stars of "star cluster Pismis 24" have pushed aside the NGC 6357 nebula gases such that all the bright stars in today's APOD diffuse nebula are simply unrelated foreground stars.
http://en.wikipedia.org/wiki/NGC_6357#Pismis_24 wrote:
<<NGC 6357 is a diffuse nebula near NGC 6334 in the constellation Scorpius. This nebula was given the name War and Peace Nebula by the Midcourse Space Experiment scientists because of its appearance. They said that in infrared images the bright, western part resembles a dove, while the eastern part looks like a skull. The nebula contains many proto-stars shielded by dark disks of gas, and young stars wrapped in expanding "cocoons".>>
Jerry: I read the most unbelievable thing about Tolstoy the other day,
did you know the original title for "War and Peace"
was "War--What Is It Good For?"!

Elaine: Ha ha.

Jerry: No, no.. I'm not kidding Elaine it's true, his mistress didn't
like the title and insisted him change it to "War and Peace"!

Elaine: But it's a line from that song!

Jerry: That's were they got it from!

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by Ann » Mon Nov 22, 2010 2:30 pm

DavidLeodis wrote:I am a bit confused (as usual :) ). Is the very bright star in the APOD part of Pismis 24 or not :?:. Clicking on the APOD brings up a larger field-of-view image that is also reproduced in an earlier post by Ann in which it states it "is another image of NGC 6357, showing more of the cluster Pismis 24". The "showing more" would seem therefore to imply that the bright star in the APOD is part of Pismis 24. Thanks for any help.
I'm not sure I can help you, but here is my take on it.

Let's start with the Orion Nebula and the well-known Trapezium cluster at the center of it.

Image

The Trapezium cluster. The five brightest stars here are the ones that power the Orion Nebula.

All right, but take a look at the upper right corner of the picture. Here is a reddish area and a notable yellowish star. This yellow star is actually a massive star in the process of forming, but it has not "broken out of its natal cocoon" yet, and it is only detectable in infrared light. (It could well be that it is detectable in X-rays. too.)

The important point is that the infrared star in Orion is younger than the stars of the Trapezium. It is not yet a fully-fledged star, and it is not a member of the Trapizium. But once it breaks out of its natal cocoon, what then? Will it be a member of the Trapezium cluster once it is a true main-sequence star? I think not, because it is younger than the members of the Trapezium and it is also physically separate from them. It is close to them but not close enough to be a part of their cluster, or so I think.

The situation in today's APOD is somewhat similar, except that the star featured in today's APOD is not an infrared star. It is detectable in visible light. The remnants of its natal cocoon are easily visible around the star, but the gas and dust does not hide the star from view. But I'd say that it is clearly younger than the members of Pismis 24. It was not born at the same time and not out of exactly the same dust cloud.

My opinion is that the star in today's APOD should probably not be regarded as a true member of Pismis 24. Then again, Pismis 24 is very distant, and it is certainly very possible that all the stars that are visible close to the obvious members of Pismis 24 were also counted as members of it by the man who named the cluster, Mr. Pismis himself.

Ann

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by DavidLeodis » Mon Nov 22, 2010 2:00 pm

I am a bit confused (as usual :) ). Is the very bright star in the APOD part of Pismis 24 or not :?:. Clicking on the APOD brings up a larger field-of-view image that is also reproduced in an earlier post by Ann in which it states it "is another image of NGC 6357, showing more of the cluster Pismis 24". The "showing more" would seem therefore to imply that the bright star in the APOD is part of Pismis 24. Thanks for any help.

PS. Lovers of diffraction spikes will like the larger image that is brought up when clicking on the APOD. :)

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by Ann » Mon Nov 22, 2010 5:42 am

As for NGC 6357, the shape of this nebula bears witness to the fact that it hosts extremely massive stars. NGC 6357 is "torn and tattered at the edges":
Another super-famous nebula is also "torn and tattered":

Image

It would appear that when the stars inside a nebula are massive enough, they produce the kind of super-furious stellar winds that simply "break the nebula apart".

Close to NGC 6357 is the more famous Cat's Paw nebula. Its rounded shape bears witness to the fact that the stars that are born inside are not as monstrously massive as those inside NGC 6357:

Image

The Cat's Paw nebula does not produce quite as massive stars as NGC 6357, and it is more rounded in shape.

Ann

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Sun Nov 21, 2010 9:08 pm

owlice wrote:
I thought the throne thing you had going on was just a joke, too, but seeing was believing!
-----------------------------------------------------------------
_____ King Henry VI, Part iii Act 1, Scene 1

KING HENRY VI: And shall I stand, and thou sit in my *THRONE*?
-----------------------------------------------------------------
_____ Measure for Measure Act 5, Scene 1

DUKE VINCENTIO: let the devil
. Be sometime honour'd for his burning *THRONE*!
-----------------------------------------------------------------

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by owlice » Sun Nov 21, 2010 6:47 pm

neufer wrote: And here I thought that that broomstick gag was just a joke. :shock:

Art Neuendorffer

P.S., Edward de Vere died on St. John's Day, 1604 and was subsequently deposed by a bald mountebank.
And I thought the throne thing you had going on was just a joke, too, but seeing was believing!

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Sun Nov 21, 2010 3:56 pm

owlice wrote:
neufer wrote:
Russian legend tells of a witches' sabbath taking place on St. John's Night (June 23–24) on the Lysa Hora (Bald Mountain), near Kiev:

"So far as my memory doesn't deceive me, the witches used to gather on this mountain, gossip, play tricks and await their chief — Satan. On his arrival they, i.e. the witches, formed a circle round the throne on which he sat, in the form of a kid, and sang his praise. When Satan was worked up into a sufficient passion by the witches' praises, he gave the command for the sabbath, in which he chose for himself the witches who caught his fancy."

The Stokowski arrangements are only rarely heard today.
The NSO performed the Stokowski arrangement summer of last year at Wolf Trap.
It was great fun! Also on the program, Carmina Burana. Fun, fun program!
And here I thought that that broomstick gag was just a joke. :shock:

Art Neuendorffer

P.S., Edward de Vere died on St. John's Day, 1604 and was subsequently deposed by a bald mountebank.

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by owlice » Sun Nov 21, 2010 2:02 pm

neufer wrote:The Stokowski arrangements are only rarely heard today, Rimsky-Korsakov's orchestratrion being the concert favorite.
The NSO performed the Stokowski arrangement summer of last year at Wolf Trap. It was great fun! They also did two other Stokowski arrangements, Schubert Ave Maria and Bach Toccata and Fugue. Also on the program, Prelude to the Afternoon of a Faun and Carmina Burana. Fun, fun program!

Re: APOD: A Massive Star in NGC 6357 (2010 Nov 21)

by neufer » Sun Nov 21, 2010 1:57 pm

APOD Robot wrote:
<<NGC 6357 houses the open star cluster Pismis 24, home to many of these tremendously bright and blue stars. The central part of NGC 6357 shown spans about 10 light years and lies about 8,000 light years away toward the constellation of the Scorpion.>>

8,000 light years would put NGC 6357
in the bright Scutum–Centaurus Arm:

http://en.wikipedia.org/wiki/Scutum%E2%80%93Centaurus_Arm wrote:
<<The Scutum–Centaurus Arm (also known as Scutum-Crux arm), is a long, diffuse curving streamer of stars, gas and dust that spirals outward from the proximate end of the long Milky Way bar. As the Milky Way is classified as a barred spiral galaxy, this feature is termed a spiral arm. It is one of two major spiral arms, and it lies between the minor Carina–Sagittarius Arm and Perseus Arm—the second major arm. The Scutum–Centaurus Arm arm starts near the core as the Scutum Arm, then gradually turns into the Centaurus Arm.

The region where the Scutum–Centaurus Arm arm connects to the bar of the galaxy is rich in star-forming regions. In 2006 a large cluster of new stars containing 14 red supergiant stars was discovered there and named RSGC1. In 2007 a cluster of approximately 50,000 newly formed stars named RSGC2 was located only a few hundred light years from RSGC1; it is thought to be less than 20 million years old and contains 26 red supergiant stars, the largest grouping of such stars known. Other clusters in this region include RSGC3 and Alicante 8.>>

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