APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

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APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by APOD Robot » Wed Jun 27, 2012 4:05 am

Image Simeis 188 in Stars, Dust and Gas

Explanation: When stars form, pandemonium reigns. A particularly colorful case is the star forming region Simeis 188 which houses an unusual and bright cloud arc cataloged as NGC 6559. Visible above are red glowing emission nebulas of hydrogen, blue reflection nebulas of dust, dark absorption nebulas of dust, and the stars that formed from them. The first massive stars formed from the dense gas will emit energetic light and winds that erode, fragment, and sculpt their birthplace. And then they explode. The resulting morass can be as beautiful as it is complex. After tens of millions of years, the dust boils away, the gas gets swept away, and all that is left is a naked open cluster of stars. Simeis 188 is located about 4,000 light years away and can be found about one degree northeast of M8, the Lagoon Nebula.

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Ann
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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by Ann » Wed Jun 27, 2012 6:29 am

APOD Robot wrote:
When stars form, pandemonium reigns.
...
The resulting morass can be as beautiful as it is complex.
I'll say! This region is one of the most beautiful parts of the sky, at least photographically. O so I think anyway.

But while it is very beautiful indeed, it is also complex and hard to understand. Let's start with the bright red arc at two o'clock. How was that thing formed? Please note that the cluster "inside" the red arc is wrapped in a cocoon of blue light. That blue light strongly suggests a reflection nebula to me. But if this little cluster is sitting in a reflection nebula, then it can contain no O-star, since O-stars are found inside emission nebulae, not reflection nebulae. But if there is no O-star here, how can this cluster power that fantastic red arc???

Here is my take on it. Note the rather bright blue star to the lower left of the red arc. I believe that this star, HD 162951, is the central powerhouse of the Simeis 188 region. If you check out the M8 link of today's APOD, you can see how the Simeis 188/ NGC 6559 region is "attached" to the Lagoon Nebula, but even so the nebulosity surrounding HD 162951 forms a center of its own.

What kind of a star is HD 162951? My software quotes sources which define this star as belonging alternatively to spectral classes O8, B0 and B6!! Apparently not too much is known about this star. I'd say, judging from the "visual appearance of the nebula", that B0 seems like a good guess. If HD 162951 belonged to spectral class O8, I think it would be "too powerful" and blow many of the rather delicate structures away. Also I think that the red nebulosity of Simeis 188 would be generally brighter. A spectral class of B6 is out of the question, at least as far as I'm concerned, since that would mean that the star would be unable to do any ionization at all.

So let's say, tentatively, that HD 162951 belongs to spectral class B0. The star is able to provide most of the faint red emission nebulosity of Simeis 188. But the star also produces a stellar wind that must be taken into account.

Now look at that red arc at two o'clock and the small cluster inside it. As I said, we can be sure that the small cluster contains no O star. We can also be sure that the cluster is very young. Note a blackish "pillar of dust" that seems to "drop down" into the cluster in today's APOD. Closer to the newborn stars the black pillar turns into a "black bow shock", blown by the stellar winds of the newborn stars.

So the stars in the small cluster are very young and still surrounded by much of their natal birth cloud. The stars also produce stellar winds, which blows the "black pillar of dust" into a "black bow shock".

Their stellar winds are also trying to blow away the dust that lies between them and HD 162951. Yes, but HD 162951 is clearly more powerful than the newborn stars in the cluster: it is brighter and hotter, and it blows harder. So when the newborn stars in the small cluster are blowing the dust in one direction, HD 162951 is blowing it in the opposite direction, so that the dust is being "slammed together" from two directions. The result is a bright arc, which is the most highly ionized part of the entire Simeis 188 region. Check out the M8 link again, to see how the red arc stands out.

And when you are looking at that M8 link, note how the Lagoon Nebula itself is surrounded by red arcs, which where produced when the stellar winds from the many O-stars in the Lagoon slammed into the surrounding medium.

Check out today's APOD again. Note that HD 162951 has produced red arcs on the other side of itself, too, not just on the side that faces the small cluster. But on the other side the "surrounding medium" was not so thick, the collision between the stellar wind and the surrounding medium was not so powerful, and the resulting level of ionization was nowhere near as high.

Ann
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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by Boomer12k » Wed Jun 27, 2012 6:50 am

Awesome!

If you look at the center...and just off to the right...you might make out an alligator mouth, and then the snout and eyes.... Alligator Nebula?

There is also a dog like head viewed from a downward angle at the bottom center...you can see the eyes and snout...

Great Job....

Still haven't had a good night for viewing with my telescope.....ho hum..... :(

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by orin stepanek » Wed Jun 27, 2012 1:03 pm

I liked today's APOD; 8-) I liked the dry ice experiment; :wink: and I like Yakety Sax! :thumb_up: :thumb_up: :thumb_up:
Click to play embedded YouTube video.
Orin

Smile today; tomorrow's another day!

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by merryjman » Wed Jun 27, 2012 2:30 pm

This is a cool picture, but the image description is copied and pasted from an image of the same nebula from 2009: http://apod.nasa.gov/apod/ap090802.html

Poor form, man.

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by nz1m » Wed Jun 27, 2012 7:12 pm

Curious what our solar system and neighborhood would look like @ 5000 light years away? Would we have "dust" and ribbons of "dark clouds"? Or just an uneventful section of uninteresting space?

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by Ann » Wed Jun 27, 2012 7:57 pm

nz1m wrote:Curious what our solar system and neighborhood would look like @ 5000 light years away? Would we have "dust" and ribbons of "dark clouds"? Or just an uneventful section of uninteresting space?
First of all, the Sun would be an extremely faint dot from 5,000 light-years away. I'll leave it to those who know how to figure out such things to figure out how bright - make that faint - it would be, but I can tell you that you would need a very large telescope indeed to see it.

There is nothing in our Solar system that would look particularly interesting from very far away. Our solar system is not particularly dusty and would not look extremely interesting in infrared light. Visually, there is even less to see from far away, as our Solar system completely lacks visible ribbons of dust, let alone reflection nebulae (and let's not even think of emission nebulae). Our Solar system looks much better close up, with its multitude of interesting planets, of which the Earth is the incomparable jewel.

The nearest object from the Sun that might look at all interesting from 5,000 light-years is the Pleiades, or so I think anyway. Of course, the Antares region is not that much farther away, at about 500 light-years away, and it contains both bright stars, dark ribbons of dust and colorful nebulae. Many bright stars in Scorpius, Lupus, Centaurus and Crux are about 400 light-years away. Otherwise, though, I can't think of many nearby clusters, associations or nebulae that would look striking from 5,000 light-years away.

The solar neighbourhood from 5,000 light-years away?

In case you are wondering, it is just a random star field.

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by nz1m » Wed Jun 27, 2012 9:27 pm

Excellent answer. Thank you. Though the star forming (an annihilating) tumultuous regions of our Milky Way and beyond are stunning optical dazzlers I suspect the tracks left by Goldilocks and her flock might be more fruitful searching Ann's random star field? Truly, no matter where we sleuth, I do suspect life trumps all and will be utterly ubiquitous. And I trust the forms she takes will logically be as spectacular and unique as our daily APOD. Keep up the great work.

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by DavidLeodis » Thu Jun 28, 2012 10:14 am

Lovely image but its explanation is causing me some uncertainty. Is Simeis 188 the whole of the nebula in the image? Is the "unusual and bright cloud arc cataloged as NGC 6559" the object to the edge at about 2 o'clock? Thanks for any help.
Last edited by DavidLeodis on Thu Jun 28, 2012 12:53 pm, edited 1 time in total.

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Ann
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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by Ann » Thu Jun 28, 2012 11:23 am

Good question. I have previously searched for a name or a designation for this colorful region, but the only name I've come across has been NGC 6559. I haven't been absolutely sure which part of this region was NGC 6559. It actually appears that the designation belongs to the red arc with the small cluster (or double star) inside. After all, the red arc is the most highly ionized part of this region and therefore the most easily detectable, and it is quite likely that no other part of this region was detected by those who compiled the NGC/IC Catalogue.

I hadn't heard the designation Simeis 188 before, either. A quick googling of Simeis 188 turned up variations of today's APOD, but no new information. Well, except this entry - don't you find this weird?

Simeis 3-188 - Pickering's Triangle supernova remnant in Cygnus

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by DavidLeodis » Thu Jun 28, 2012 12:56 pm

Thanks Ann for your response, which is appreciated. It's good to know that I'm not the only one that is uncertain. :)

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Re: APOD: Simeis 188 in Stars, Dust and Gas (2012 Jun 27)

Post by Ann » Thu Jun 28, 2012 1:56 pm

Check out this page. Here you can read that only two Simeis objects are known to Google, Simeis 147 and Simeis 57. (We may note that Simeis 188 has become known after Dieter Willasch's image became the APOD of June 27, 2012, and Simeis 3-188 has made the cut, too.)

A person calling him(?)self sgottlieb, scholastic sledgehammer, provides the following information about the Simeis catalog:
The actual journal articles are not available online though a listing of the pertinent Simeis publications is here. The lists were published in the early '50's in the Ukrainian "Bulletin of the Crimean Astrophysical Observatory" (Izvestiya Krymskoi Astrofizicheskoi Observatorii).
Just so you know. :shock:

Ann
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