Endzeit by ~N3UR0N heavily reminds me of the movie "Sunshine". There is a similar beautiful sun floating everything with light. Lean back for a moment and enjoy the warm colors on full-screen!! (
because the sun is whiter in the center it made me think that it was a shockwave semi-transparent and the whitest region was the source of the light, also the bcakground looks like the sun so it made me think that I was seeing a little of the background too. I hope you understood that.
besides that the rest looks awesome, also the the degree of the background looks almost like a painting because of its high opacity (or less stars behind it)
A sun should be whiter near its center (despite how most artists interpret the look of the sun in their pieces), simply because the center is where you're "looking through" most of the sun. It's the area with most gas and highest density - and should therefore be the brightest area of the sun.
just keep layering single brush taps on various layer modes in photoshop. starting with a large one and working to a smaller size. with various tones of orange yellow and sometimes red. using modes like linear dodge and color dodge etc.