Heh heh heh, the wonders of special effects!

Of course, you wouldn't be able to see a laser beam in space, either (lasers are only visible when there is dust or fog or something in the way to scatter the beam off of, just as you can't "see" rays of sunlight without such helpers either).

Making a beam similar to what the Death Star uses in Star Wars with a laser is impossible. However, if the beam were composed of charged particles instead (i.e. a plasma beam), then you could potentially shape it with magnetic fields. Plasma would also be incandescent, so you COULD see it in space, unlike a laser (although it still would make no sound)!

That said, the ability to focus even ONE beam of plasma - let alone several - poses such immense engineering challenges that nobody currently has any real idea how to make a weapon out of it. That's not to say that it isn't possible, however, just far enough beyond our current level of technology that Clarke's Third Law applies ("any technology sufficiently advanced will be indistinguishable from magic").