NGC 6888: The Crescent Nebula (APOD 2009 Sept 15)

[P.King]

I see what appears to be a brown foreground object right smack in the middle of this photograph. I presume the Isaac Newton Telescope would not produce an artifact like this if it was not there. There appears to be a wisp of another such a blob to the upper right.

Does anyone know what this is?

[azutjw]

Sighting confirmed. My first thought is a globule of denser material Does anyone know if our line-of-sight is polar or equatorial, or something in between?

[bystander]

http://apod.nasa.gov/apod/ap090915.html

I see what appears to be a brown foreground object right smack in the middle of this photograph. I presume the Isaac Newton Telescope would not produce an artifact like this if it was not there. There appears to be a wisp of another such a blob to the upper right.

Does anyone know what this is?

I don't know what it is, but it also shows up on 2008 Aug 13, (image rotated clockwise).
Other images: 2007 Nov 11, 2003 Oct 16, and 2003 Apr 15.

[Chris Peterson]

Sighting confirmed. My first thought is a globule of denser material Does anyone know if our line-of-sight is polar or equatorial, or something in between?

It's just a dust globule- there are several seen in this nebula. The Crescent is at declination +38°, so it is neither equatorial nor polar. But that doesn't really matter; the dust is part of the nebula, not an object between us and it (of course, it does lie on our side of the nebula, or we'd see it lit, not silhouetted).

[azutjw]

OK, now you've really piqued my interest. First, the latitudinal orientation I was speaking of refers to the star relative to the line-of-sight, not the line-of-sight relative to us, to wit: any idea which way the axis of the source star is oriented? Second, thanks, dust globule was my first guess as to the nature of the object, but - -

There really aren't any others showing in the same nebula. There are similar regions, but none so large, so clearly defined in all directions, so 'separate' from all other 'structures' in the nebula. Could someone offer some learned speculation on the mechanism that would generate such an un-ordinary object?

[Chris Peterson]

OK, now you've really piqued my interest. First, the latitudinal orientation I was speaking of refers to the star relative to the line-of-sight, not the line-of-sight relative to us, to wit: any idea which way the axis of the source star is oriented?

No idea. It may not have been determined- stellar orientation is usually not known.

There really aren't any others showing in the same nebula. There are similar regions, but none so large, so clearly defined in all directions, so 'separate' from all other 'structures' in the nebula. Could someone offer some learned speculation on the mechanism that would generate such an un-ordinary object?

I disagree about whether there are others. I see several similar globules. Certainly, the one in the center appears to be the best defined, but that may be an illusion resulting from its strong back lighting. But whether it is the most distinct or not, other such dust/molecular gas clouds are present. Small globules like these typically contain several solar masses of material, and surround new star forming regions. Whether that's the case here, however, I don't know. It sure looks like the sort of globules seen in other nebulas.

[azutjw]

OK, I can accept that. Thanks.