i got a sun i’m trying to make but how can I add solar flares to it? and radiance so it actually looks hot

How large is the area you want to see the star from, and explore around? Generally the effects you’d want would be done by using a Post Processing Volume, which among many visually awesome things, will give you specific control of lens flares. Using some bloom settings you could also give it some heat and radiance, though it would apply this effect to everything rendered while you’re in the volume. Going this route would keep light radiance consistent, but may not be 100% what you’re wanting