APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

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APOD Robot
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APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by APOD Robot » Thu Sep 10, 2015 4:07 am

Image NGC 4372 and the Dark Doodad

Explanation: The delightful Dark Doodad Nebula drifts through southern skies, a tantalizing target for binoculars in the constellation Musca, The Fly. The dusty cosmic cloud is seen against rich starfields just south of the prominent Coalsack Nebula and the Southern Cross. Stretching for about 3 degrees across this scene the Dark Doodad is punctuated at its southern tip (lower left) by globular star cluster NGC 4372. Of course NGC 4372 roams the halo of our Milky Way Galaxy, a background object some 20,000 light-years away and only by chance along our line-of-sight to the Dark Doodad. The Dark Doodad's well defined silhouette belongs to the Musca molecular cloud, but its better known alliterative moniker was first coined by astro-imager and writer Dennis di Cicco in 1986 while observing Comet Halley from the Australian outback. The Dark Doodad is around 700 light-years distant and over 30 light-years long.

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Ann
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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by Ann » Thu Sep 10, 2015 5:07 am

I, too, love that name, the Dark Doodad. :D

And I think that lovely bright blue star right next to the Dark Doodad is Alpha Musca.

And while I was never that much of a Batman fan, preferring Superman instead, I do look forward to the superhero bonanza of tomorrow's APOD! :D

Ann
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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by Nitpicker » Thu Sep 10, 2015 6:16 am

Ann wrote:I, too, love that name, the Dark Doodad. :D

And I think that lovely bright blue star right next to the Dark Doodad is Alpha Musca.

And while I was never that much of a Batman fan, preferring Superman instead, I do look forward to the superhero bonanza of tomorrow's APOD! :D

Ann
I think the blue star is Gamma Muscae, mag 3.8. According to Stellarium, it appears combined with two other mag ~7 stars, unresolved at this scale. The separations are all less than 2 arcmin, but I don't know if they are gravitationally related.

Beautiful APOD. I never knew the Doodad was there, though I just spotted a much less obvious version in one of my own, wider images.

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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by Joe Stieber » Thu Sep 10, 2015 1:18 pm

Nitpicker wrote:I think the blue star is Gamma Muscae, mag 3.8. According to Stellarium, it appears combined with two other mag ~7 stars, unresolved at this scale. The separations are all less than 2 arcmin, but I don't know if they are gravitationally related.
The bright bluish star is indeed Gamma Muscae, but the two magnitude 7 flanking stars that appear in Stellarium are probably some sort of database error since neither of them appear in SkyTools or SkySafari. Besides, a magnitude 11 star about 3 arc minutes from Gamma shows clearly in the full-size image, so I think the magnitude 7 stars would be visible if they were actually there.

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Ann
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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by Ann » Thu Sep 10, 2015 2:12 pm

You are both absolutely right, Nitpicker and Joe Stieber. That is indeed Gamma Musca. And I agree with Joe, there are no seventh-magnitude stars flanking it.
Centaurus and Crux.
Credit: Akira Fuji/ David Malin images
Gamma Musca is a member (and a bit of an outlier) of the Sco-Cen association, the nearest loose scattering of massive blue stars. The distance to Gamma is 325 light-years, almost exactly the same as the distance to one of the grandest members of the Lower Sco-Cen association, Acrux, the Alpha star of the southern Cross. Fascinatingly though, while the Sco-Cen association is widespread and rich - it clutters up Centaurus and Lupus with blue brilliance and really makes its presence known in Scorpius and Crux - I can only think of a single O-type star (O9.5V) that is a member of that association, and that is the fainter component of binary star Sigma Scorpii. It seems probable that the Sco-Cen association only ever produced one O-type star that put its B-type brethren far behind it, and that is Antares. Antares is now a red supergiant, of course!

Interestingly, the Orion association seems less rich than Sco-Cen, but its brightest and most massive members outshine and outweigh the brightest and most massive ones in Sco-Cen. But perhaps Orion is every bit as rich in massive blue stars as Sco-Cen, but its members seem far less spread out in the sky, because they are farther away.

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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by starsurfer » Thu Sep 10, 2015 3:06 pm

APOD Robot wrote:The dusty cosmic cloud is seen against rich starfields just south of the prominent Coalsack Nebula and the Southern Cross.
This widefield image by the CEDIC team shows the Dark Doodad in the context of its surroundings. Also a wider image of the Dark Doodad would show multiple cometary globules.

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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by Nitpicker » Thu Sep 10, 2015 11:22 pm

Joe Stieber wrote:
Nitpicker wrote:I think the blue star is Gamma Muscae, mag 3.8. According to Stellarium, it appears combined with two other mag ~7 stars, unresolved at this scale. The separations are all less than 2 arcmin, but I don't know if they are gravitationally related.
The bright bluish star is indeed Gamma Muscae, but the two magnitude 7 flanking stars that appear in Stellarium are probably some sort of database error since neither of them appear in SkyTools or SkySafari. Besides, a magnitude 11 star about 3 arc minutes from Gamma shows clearly in the full-size image, so I think the magnitude 7 stars would be visible if they were actually there.
Right you are. Thanks.

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Re: APOD: NGC 4372 and the Dark Doodad (2015 Sep 10)

Post by Boomer12k » Fri Sep 11, 2015 12:05 am

Such a great image...
"Doodad, doodad, in the sky....how I wonder....who or why...." something, something....Ok, got to work on that....

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