This is a tutorial aimed at beginners. I will show you how to use Photoshop to make a spiral galaxy. Use this for your document setup:
Then fill the background with the color of your choice; a really dark color works best. I’ve selected a dark blue. Next, create a new layer and choose the Elliptical Marquee Tool. Set Feather at the top to 50px. Draw a round selection like the one below, and make sure some space is left at the top and bottom. Hold down Shift while drawing to make a perfect circle.
Type “D” as a shortcut to set foreground and background to black and white. Click Filter >> Render >> Clouds. Change the new layer’s Blending Mode to Soft Light.
Hit Control + T to change to Free Transform Mode. Change to Warp Mode and select Twist. Set the Bend to -95%.
Duplicate the layer (Ctrl + J). While the new layer is selected, repeat the twist transformation (using the same settings you just used) twice.
Select both Spiral layers and change to Free Transform mode (Ctrl + T). Hold Ctrl and move the anchor points to alter the galaxy. Use the image as a guide.
You may to resize your galaxy; just select both layers using CTRL or Shift. Hit CTRL+T, hold shift to keep scale, and then resize. Viola!