Let's take a look at how I did this using motion blur. Follow the steps as follows:
Open an image that has a lot of high lights or sunlight.
(In this image I adjusted levels.)
Create 2 copies of the image in the layers palette. (Drag the layer down to the blank layer icon in the layer palette 2 times.)
Select top layer - Filter blur motion blur 45 distance maximum
At this point you'll have something that looks like the middle photo.
Select top layer. In the Blend Mode select Screen
Merge top layer down (Layer - merge down)
Image adjustment Exposure - change the gamma settings to get the overall lighting. I made mine darker since Screen Mode tends to over lighten.
Try this procedure on any photo that has some nice highlights or sunshine in it. You'll be surprised what professional looking star burst effects you can get.