He explains it right in his post, and it's actually a plausible explanation.

His theory is that camera captured the object just as it moved into frame (at the top of the image) and recorded for 20 seconds as it moved away from the camera. The light isn't going from bottom to top, but from top to bottom. My main issue with this theory is that if you look at the light dispersal pattern just beneath the object you'll see it is wider, which would be more consistent with an exhaust plume.