Do it in illustrator. You can blur it up and do whatever in photoshop afterwards plus you'll have the shape as a smart object which is something small that people overlook. Here's a tutorial that helped jog my memory.
http://hughroper.com/Tips/675/illust...starburst-rays
Or you could just go here and download a brush that does it for you.
http://vector-art.blogspot.com/2007/...r-brushes.html
I would suggest learning it in illustrator so you don't have to rely on a brush and plus you can just save it in awesome vector to use time and time again and alter how you wish.
I did this in like five minutes so it might take you a bit longer in order to get it exactly how you want it. I don't really know the history behind the rising sun so I don't know if there are any exact rules to the numbers of lines extruding from the circle. Hope it helps.