here's what we're going to make:
i'm assuming you already have your own star image (doesn't matter if it has other things in the background, and all you want to make is the tendrils coming out from it.1 ) first create a new image, 800 x 600 for variety, and do filter > render > clouds. then whack one or two filter > render > difference clouds onto it, and you'll end up with something like this:
2 ) then press ctrl + L to bring up the levels window, and bring the left arrow toward the right of the bar, giving you that well-known "lightning" effect. press OK. you should get something like this:
3 ) now go to your "star" image, create a new layer and name it "glow". Select a circle around the star, out to where your flares are going to finish. ctrl + alt + d to feather it about 20 pixels, and select the brush tool. choose a nice orange colour, close to the colour of your star, and set the opacity to around 10%. brush all over that selection, to give you the "foundation" of the flare area, which will help the effect to work better.
this should give you something along these lines:
4 ) next, select small areas of your clouds image, which have branches, end points, etc. and copy them into a new layer named "flares" on your star image.
right now, you'll have an image like:
5 ) now change the blending mode of the "flares" layer to "colour dodge". this will make the flares turn the colour of your foundation, and the black disappear. you can adjust the opacity of the flares layer to suit, and adjust size, etc. as well. i used three separate flares layers, with different opacities, to get my image.
if the flares look a little too strong, give it a gaussian blur of a few pixels, until it's softer.
6 ) essentially you're done right there, but if you want to make your flares blend more smoothly into the star image, grab the smudge tool, and select the "flares" layer again. Smudge the tips of the flares into a place nearby on the star that's of a bright white colour. this way it looks like they're coming out of the star, not just hovering around it.
and there you have it, some nice flares to go with your space-themed image.
i overused mine a bit, so don't be afraid to use the same effect but to a smaller extent, or lower the opacity even more.