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Whilst processing a recently acquired image of M104, I noticed two faint extended objects. These are indicated by the blue arrows in the image below, which has had the contrast greatly boosted to make them visible. I'm pretty sure they are both real and DSOs (not something transient) as they also appear - unlabelled and unidentified - in the image of M104 in the Stellarium mobile app. However, I can't find any record of what they might be. They're not included in annotations from ASTAP (which are shown in the image below), even with the extended galaxy catalog. They don't show in the Stellarium desktop app, or in the annotations provided by astrometry.net. Appreciate any suggestions!  |
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Try with Aladin: https://aladin.u-strasbg.fr/ The brighest one is catalogued as: [C83] NGC 4594 DW1 |
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even Aladin-Lite does not have data on the second object. @James Tickner please provide an image with no annotation for checking. CS Gernot |
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Thanks for the advice about Aladin - I hadn't come across that resource before. Very useful! It confirms that the brighter object is [C83] NGC 4594 DW1 as you mentioned, which I understand to mean that this is a dwarf galaxy associated with NGC 4594 (M104) which is referenced in Caldwelll's 1983 paper. It's curious that a galaxy of this size and (relative) brightness - mag 17.2 - doesn't get a PGC entry or appear in HyperLEDA. Poking around in Aladin there are a few 'hits' on the second object, but it's less clear (to me at least) what they refer to. Here's a link to the original image as requested: https://astrob.in/m4ds4k/0/ |
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Hi James, here is your image annotated in PI with some more catalogs activated but the object does not show up.  You can load many star catalogs into PI for the annotation function. For identification of asteriods however it is needed to have the time when the picture was taken to be taken into account.  So it is a matter of finding the right catalog ... Sorry but there is no quick answer. CS Gernot |
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Thanks Gernot! I don't have PI yet so it is good to see that capability. My first thought (hope!) when I saw the unknown object was a comet or asteroid, but nothing came up in ASTAP's solar system object identification. The fact that both objects also show in historical images taken by others pretty much confirms they are both DSO. The second object is very faint and also partially overlaps with a foreground star, so it is hard to make out. I guess this will remain a mystery for now. |
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James, the deepest DSO database I am aware of is the NASA/IPAC extragalactic database. Unfortunatelly I could not find entries for those DSO, but it might be useful for future research work. CS, Fritz |
