Article doesn't have a good description.
My guess is you take a bunch of timelapse frames of the same sky.
Then you overlay them at offsets in different directions which would keep any moving objects in the same place.
Picture doing 36000 sequences of overlays:
360 degree variation in 0.1 degree increments at 10 different radial velocities
Most of those sequences will just show blurred gray washout, but if you happened to hit the right direction as a moving object at the right speed, your overlaid image sequence will effectively keep the moving object in the same spot of the frame, which will result in the average brightness for that pixel or pixles to be higher than the surrounding blurs.
Just a guess...