1
Create a new image, and in the Layers window, make a new
layer.

Now, in the Photoshop tools bar, grab the Rectangular Marquee tool.

Make one thin selection spanning from the top of your image to the bottom. Then, holding down Shift, draw a few more vertical selections spanning from the top to the bottom of the image.

2
Now, select an appropriate foreground color for your starburst. I've chosen blue.

Fill the selection, by pressing Alt+Backspace, on the keyboard.

Deselect, by pressing Ctrl+D.

3
In the menu select:

Filter > Distort > Polar Coordinates...

Select Rectangular to Polar, hit OK and enjoy!