Odd black spot
I've seen this on at least one other image.
Is there an image artifact at 4 o'clock on the rim? It has the appearance of a bubble or black spot.
No joy doing a search for terms black, spot, or bubble (I think that was my prior comment).
It's very hard to say, the galaxy is extremely faint in its outer parts, but I think it's an artifact.
Here is the same galaxy in DR10 (same data, different processing); has the black spot disappeared? I think so.
Link posted above is bad. Image checked in DR9, and black spot is present in that image as well.
It looks like an bubble (ring shape at periphery) or a black spot. I thought it could be a sort of gravity lensing.
This may be an artifact, since it appears completely black in a relatively illuminated area. Perhaps a dead pixel in the CCD? I thought that was pretty unlikely though.
Thanks for reviewing this.
The SDSS DR8 and DR9 images are the same. As far as I know, SDSS has produced three, independent, sets of Explore/JPG images, all from the same raw data1 ... which means that differences in appearance, between the three, are to some extent artifacts of the different processing done on the raw data.
There certainly are 'bad pixels', but they are (very cleverly) masked out, in the photometric processing pipeline. It's possible that one slipped by, in this case.
It's not so much that my link is bad; rather, the SDSS DR10 image server - which creates the JPGs - is "having an off day" 😉 I'm not surprised, really; DR10 went live only a few days ago, so the load must be high, and the many bugs not yet ironed out ...
1 It's not really the raw data; rather it's the corrected 'intensity' values for each pixel (in each band/filter) from the CCDs in the camera. This data is available from the SDSS website as a (rather large) FITS file (five, actually; one per filter)
Thanks for the info. Good luck with Phase II. I hope to assist, but (for now) the dashboard interface does not appear to be functioning for my configuration.