UFO Sighting in Mogi das Cruzes, São Paulo on June 12th 2015 – Strange green-blue light shown after download pics to computer

I was taking some pictures of the beautiful night sky, Venus and Jupiter were easily visible right after the sunset. I took some long exposures, and noticed on the camera screen a green-blue glowing object, but assumed that it was some sky element, such a star cluster or something alike. I took around 8 pictures of the couple planets and when I downloaded to laptop I noticed the "orb" and tryed to figure out what it was on several online starcharts, including the free stelarium software. For my surprise, nothing there to spot like the pictures...I was wondering what is this, if I caught a simple sky object (I could not find it on strelar charts) or is something else? The pics were taken around 19:20 hours, thanks a lot. No sound, and disapeared in the sequence photos of the same place. I used a Nikon D40X with several exposures and different ISO. Thanks a lot for your attention, my kindest regards Erico