I would not bother trying to fix that manually – since it is such a simple image, why not recreate it from scratch, and fake it?
– add a solid color layer with the orange background colour
– add a white vector circle with perhaps a yellow stroke. Convert to a smart object, and apply a slight gaussian blur to fade out the edge
– add a larger circle in the background, apply a circular gradient and pick up the colours from the original.
Some fine-tuning, and done! For a more realistic effect I also added a bit of granularity to the edges for the “Sun”, and applied a bit of noise.

PS I did this in Photoline, but the process is exactly as I described. This is arguably easier & quicker to pull off in Photoline than in Photoshop, because of Photoshop’s rather horrible outdated and quirky gradient editor. In Photoline any gradient can be edited “in place”.
/*—————————————————-*/
System: Win7 64bit – i7 920@3.6Ghz, p6t Deluxe v1, 48gb (6x8gb RipjawsX), ATI 7970 3gb, EVGA 590 3GB, Revodrive X2 240gb, e-mu 1820. Screens: 2 x Samsung s27a850ds 2560×1440, HP 1920×1200 in portrait mode