This image below (from 2014-01-19) isn’t a mystery. We’re seeing a bright star through some secondary optical path. The star is out of focus — as secondary images normally are — and we see shadows from the optical and support structures.
Can we tell what star it is? The nearest really bright star is Spica, which has coordinates (in decimal degrees) of about (RA,Dec)=(201.298,-11.161). This image is centered at (200.01,-9.356). That’s 2 degrees, a pretty long way away–maybe 4000 pixels in the image. But the DSS plates from which these data are taken are a full 6 degrees on a side, so Spica could be in the field of view.
In fact if we look at the plate that seems to enclose this location (labeled s719), it has a center at (200.658,-10.261). That’s just about the center of the two locations. It’s pretty common that there will be an artifact at a location like this with some kind of symmetry with the real location. So Spica it is. Sometimes the obvious answer is the right one.