The box crossing the 8 foot opening is rather shallow (in height) and it seems unlikely there's really a beam in there. If there's no true beam there now that raises the probability that you can freely make the opening wider.
There are several things you could do to find out whether there's a beam in that box. One is to pull the drywall off one side and have a look. (I'm guessing it may be 2 or 3 2x4s nailed up into the bottoms of the trusses and serves only to support the drywall.)
If there is a beam in the box there'll be two or more studs at the left and right sides of the opening to support it. Probe the sides of the opening, ie between the light switch and the opening, to see how much wood is there. You could do it with a stud finder, a nail, a drill, etc.
Another thing to check is the roof trusses. Look at how the webbing members are arranged in the truss. Do a pair of webs come together and rest directly on top of this wall? If so the wall is likely bearing, but if not, the wall is likely non-structural.