APOD: LDN 988 and Friends (2015 Sep 24)

APOD Robot · Post by **APOD Robot** » Thu Sep 24, 2015 4:07 am

LDN 988 and Friends

Explanation: Stars are forming in dark, dusty molecular cloud LDN 988. Seen near picture center some 2,000 light-years distant, LDN 988 and other nearby dark nebulae were cataloged by Beverly T. Lynds in 1962 using Palomar Observatory Sky Survey plates. Narrowband and near-infrared explorations of the dark nebula reveal energetic shocks and outflows light-years across associated with dozens of newborn stars. But in this sharp optical telescopic view, the irregular outlines of LDN 988 and friends look like dancing stick figures eclipsing the rich starfields of the constellation Cygnus. From dark sites the region can be identified by eye alone. It's part of the Great Rift of dark clouds along the plane of the Milky Way galaxy known as the Northern Coalsack.

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Ann · Post by **Ann** » Thu Sep 24, 2015 4:42 am

What a nice image!

I, of course, love the subtle blue reflection nebulosity in the image, caused by tiny dust particles scattering light, preferably blue light, in our direction. But at lower right there are two small orange patterns, showing the reverse side of dust: it preferentially scatters blue light, but when the blue light is scattered away from us, the light that reaches us is orange. Or red. Or the light doesn't reach us at all, as when dark patches of dust completely block the visible light that tries to penetrate.

At lower left in today's APOD, the background light is subtly red. This is likely faint Ha emission.

Ann

NCTom · Post by **NCTom** » Thu Sep 24, 2015 10:31 am

At the end of one of the legs of the dancing figure upper left of center is an encircled star. I know too little to hazard a guess. Is this some form of planetary nebula?

Joe Stieber · Post by **Joe Stieber** » Thu Sep 24, 2015 1:02 pm

NCTom wrote:At the end of one of the legs of the dancing figure upper left of center is an encircled star. I know too little to hazard a guess. Is this some form of planetary nebula?

That would be V1331 Cyg, see: http://www.spacetelescope.org/images/potw1509a/

With its helical appearance resembling a snail’s shell, this reflection nebula seems to spiral out from a luminous central star in this new NASA/ESA Hubble Space Telescope image.

The star in the centre, known as V1331 Cyg and located in the dark cloud LDN 981 — or, more commonly, Lynds 981 — had previously been defined as a T Tauri star. A T Tauri is a young star — or Young Stellar Object — that is starting to contract to become a main sequence star similar to the Sun.

What makes V1331Cyg special is the fact that we look almost exactly at one of its poles. Usually, the view of a young star is obscured by the dust from the circumstellar disc and the envelope that surround it. However, with V1331Cyg we are actually looking in the exact direction of a jet driven by the star that is clearing the dust and giving us this magnificent view.

This view provides an almost undisturbed view of the star and its immediate surroundings allowing astronomers to study it in greater detail and look for features that might suggest the formation of a very
low-mass object in the outer circumstellar disc.

BTW, I don't think this region is the Northern Coalsack, which is south-southeast of Deneb (Alpha Cygni), under the southern wing of Cygnus. The pictured region, with LDN 988 and 981, is northeast of Deneb and outside of the usual stick figure of Cygnus. It looks more like the Le Gentil 3 region to me.

neufer · Post by **neufer** » Thu Sep 24, 2015 1:49 pm

Joe Stieber wrote:
NCTom wrote:
At the end of one of the legs of the dancing figure upper left of center is an encircled star.
I know too little to hazard a guess. Is this some form of planetary nebula?
That would be V1331 Cyg, see: http://www.spacetelescope.org/images/potw1509a/

https://en.wikipedia.org/wiki/The_Adventure_of_the_Dancing_Men wrote:
[b][color=#0000FF]Dancing Men diagram drawn by Conan Doyle[/color][/b]
<<Sir Arthur Conan Doyle ranked "The Adventure of the Dancing Men" third in his list of his twelve favorite Holmes stories. This is one of only two Sherlock Holmes short stories where Holmes' client dies after seeking his help. (The other is "The Five Orange Pips.")

Synopsis: Mr. Hilton Cubitt of Ridling Thorpe Manor in Norfolk visits Sherlock Holmes and gives him a piece of paper with this mysterious sequence of stick figures. The little dancing men are at the heart of a mystery which seems to be driving his young wife Elsie Patrick to distraction. Holmes tells Cubitt that he wants to see every occurrence of the dancing men. They are to be copied down and brought or sent to him at 1331V Swan Street. Cubitt duly does this, and it provides Holmes with an important clue. Holmes comes to realize that it is a substitution cipher. He cracks the code by frequency analysis.>>

Ann · Post by **Ann** » Thu Sep 24, 2015 3:02 pm

Joe Stieber wrote:
NCTom wrote:At the end of one of the legs of the dancing figure upper left of center is an encircled star. I know too little to hazard a guess. Is this some form of planetary nebula?
That would be V1331 Cyg, see: http://www.spacetelescope.org/images/potw1509a/
With its helical appearance resembling a snail’s shell, this reflection nebula seems to spiral out from a luminous central star in this new NASA/ESA Hubble Space Telescope image.

The star in the centre, known as V1331 Cyg and located in the dark cloud LDN 981 — or, more commonly, Lynds 981 — had previously been defined as a T Tauri star. A T Tauri is a young star — or Young Stellar Object — that is starting to contract to become a main sequence star similar to the Sun.

What makes V1331Cyg special is the fact that we look almost exactly at one of its poles. Usually, the view of a young star is obscured by the dust from the circumstellar disc and the envelope that surround it. However, with V1331Cyg we are actually looking in the exact direction of a jet driven by the star that is clearing the dust and giving us this magnificent view.

This view provides an almost undisturbed view of the star and its immediate surroundings allowing astronomers to study it in greater detail and look for features that might suggest the formation of a very
low-mass object in the outer circumstellar disc.

The only star that looks encircled to me in today's APOD is the lovely bright blue star at top left, at 11 o'clock. It is surrounded by a beautiful blue halo. I think that the star might be SAO 33034. If I have managed to identify V1331 in today's APOD, it doesn't look obviously encircled to me.

But thanks a lot for the fascinating link, Joe Stieber!

Ann

EDIT: Oh! I found it!

neufer · Post by **neufer** » Thu Sep 24, 2015 3:31 pm

http://skycenter.arizona.edu/gallery/Nebulae/V1331Cygni

BMAONE23 · Post by **BMAONE23** » Thu Sep 24, 2015 5:07 pm

Ann wrote:What a nice image!

I, of course, love the subtle blue reflection nebulosity in the image, caused by tiny dust particles scattering light, preferably blue light, in our direction. But at lower right there are two small orange patterns, showing the reverse side of dust: it preferentially scatters blue light, but when the blue light is scattered away from us, the light that reaches us is orange. Or red. Or the light doesn't reach us at all, as when dark patches of dust completely block the visible light that tries to penetrate.

At lower left in today's APOD, the background light is subtly red. This is likely faint Ha emission.

Ann

Interestingly this slightly redder region seems to end abruptly at the Left edge of the image in a seemingly impossible straight line. Probably an artifact from the filters used with the Red band not including that linear region

starsurfer · Post by **starsurfer** » Thu Sep 24, 2015 5:45 pm

BMAONE23 wrote:
Ann wrote:What a nice image!

I, of course, love the subtle blue reflection nebulosity in the image, caused by tiny dust particles scattering light, preferably blue light, in our direction. But at lower right there are two small orange patterns, showing the reverse side of dust: it preferentially scatters blue light, but when the blue light is scattered away from us, the light that reaches us is orange. Or red. Or the light doesn't reach us at all, as when dark patches of dust completely block the visible light that tries to penetrate.

At lower left in today's APOD, the background light is subtly red. This is likely faint Ha emission.

Ann
Interestingly this slightly redder region seems to end abruptly at the Left edge of the image in a seemingly impossible straight line. Probably an artifact from the filters used with the Red band not including that linear region

No there is faint hydrogen alpha emission in the region and is visible in other images such as this one by Fabian Neyer.

saturno2 · Post by **saturno2** » Thu Sep 24, 2015 10:26 pm

LDN 988
Dancing stick figures
Interesting image.

NCTom · Post by **NCTom** » Fri Sep 25, 2015 12:07 pm

Thanks, everyone. I've rarely been introduced to a "Young Stellar Object" especially with this clear a view. Fascinating creatures!

DavidLeodis · Post by **DavidLeodis** » Fri Sep 25, 2015 8:24 pm

In the annotated version brought up through the "LDN 988 and friends" link it has LDN and LBN labelled nebulae (that information is also available in Rafael's website). I assume that LDN will be Lynds Dark Nebula but what does LBN stand for? (Lynds Black Nebula??).

neufer · Post by **neufer** » Fri Sep 25, 2015 8:36 pm

DavidLeodis wrote:
In the annotated version brought up through the "LDN 988 and friends" link it has LDN and LBN labelled nebulae (that information is also available in Rafael's website). I assume that LDN will be Lynds Dark Nebula but what does LBN stand for? (Lynds Black Nebula??).

Lynds Bright Nebula

DavidLeodis · Post by **DavidLeodis** » Fri Sep 25, 2015 11:11 pm

neufer wrote:
DavidLeodis wrote:
In the annotated version brought up through the "LDN 988 and friends" link it has LDN and LBN labelled nebulae (that information is also available in Rafael's website). I assume that LDN will be Lynds Dark Nebula but what does LBN stand for? (Lynds Black Nebula??).

Lynds Bright Nebula

Thanks for your help neufer

. My guess of Lynds Black Nebula could hardly have been more wrong!

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APOD: LDN 988 and Friends (2015 Sep 24)

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