Very interesting, Geck.
Let's look at the thing. It is white in color. Therefore it is not a far-away background object, which are yellowish or orange.
NGC 5238 is not white in color, however. Its bright stars are mostly blue, with a few bright yellow-orange stars in the mix. The faint stars of NGC 5238 are mostly yellowish. The bright stars are undoubtedly young and quite bright stars, many of spectral class B and maybe even O, as can be deduced from the widespread presence of green (really red) emission nebulae. A small number of the bright yellow-orange stars just might be young M-type giants or (lesser) supergiants, or at least bright young K-type giants or supergiants. The faint yellowish stars are probably (that would be my guess anyway) modest old red giants.
The mightiest cluster of young blue stars is of course the structure to the lower left of the other blue stars in NGC 5238. There is a mighty green (really red) arc of nebulosity to the upper right of it. As for the cluster itself, it has an obvious core, and there are more widely scattered stars apparently flowing away in the opposite direction than the green arc of nebulosity. To me this suggests a young compact cluster whose outer parts are either scattering away, or else they are the products of earlier rounds of star formation.
My software calls this structure PGC 47857, which means it has been classified as an independent galaxy. I really don't think it looks like a galaxy - at best it is a very proto-proto-galaxy! - but please note that the green arc "above" this cluster looks a bit like a bow shock. It is just faintly possible that the cluster was formed farther away from the core of NGC 5238 than its present location, and then it just might have been acted on by the gravity of NGC 5238 so that it is now moving in towards the core, creating a bow shock in front of it. (Of course the green arc might just be the brightest part of the emission nebula surrounding this cluster.) Note that the core of NGC 5238 is obviously brighter than the cluster that may be moving towards it. The core is also slightly bluish in color. This may account for the fact that my software says that the effective B-V color of NGC 5238 is 0.130, which is absolutely extremely blue for a galaxy.
Let's return to the elongated globular cluster. It is an extremely high surface brightness object, and unlike any of the background galaxies, it appears to be surrounded by a halo of stars. This clearly suggests that the object is a globular cluster, although a very strange one.
Here is my guess. I would guess that the elongated globular cluster just possibly might be a comparatively high-metallicity cluster, so that it lacks blue horizontal stars, similar to 47 Tucanae.
47 Tuc is quite white in color, compared to the bluish color of apparently neighbouring dwarf galaxy, the Small Magellanic Cloud. The white color of the globular cluster next to NGC 5238, compared with the mostly bluish color of the dwarf galaxy itself, might be explained in a similar way.
(There is by the way another globular cluster in the picture of NGC 5238, right next to the black area at upper right. This makes the appearance of NGC 5238 eerily similar to the
SMC and the two globular clusters that are seen in the direction of it, 47 Tuc and NGC 362.)
But what about the elongated shape of the cluster? Here is my guess. Quite a long time ago, this cluster might have merged with another globular cluster in a way that induced a disk formation in the cluster. And if it didn't merge with another globular cluster, then perhaps it merged with something else, like possibly a concentrated chunk of dark matter. Or something. All the messiness of tidal tails and other kinds of untidiness are gone by now, but the elongated disk shape of the globular cluster remains.
Just my two cents.
Ann
