I'm not sure if this is right, but if you have the measure of the degree created by the sun, and you know that another one of the angles is 90 degrees then you can find the last remaining angle by taking the sum of the two and subtracting it from 180. Then you can you tangent of the sun to find the opposite side, since you know the side labeled y. Then all you have to do is the pythagorean theorem to find the side that is representing the distance from the sun to the shooting star.
Hope this helps!