Just a ghost flare effect:
It's a very common source for UFO misidentification and one of the various flare effects that occurs when a bright light source is photographed or
Usually, people who take photos/videos with this effect don't know how it's done and haven't seen anything with naked eye.
I'll explain here how it works in an optical and scientific way with some examples:
The flare is generally due to the presence of a protective filter in the camera, after the lens. The flare is a mirror ghost of the original bright
object, with the image center serving as a point of symmetry (or point reflection
All dimensions are, most of the time, perfectly preserved, which suggests that reflections at planar surfaces are responsible.
Let's see how it works with the figure below:
Black arrows indicate the light rays of a distant bright light source that form a regular image point on the film (1). Values for the reflectance of
undeveloped photographic film vary from 15% to 40% [see sources 1,2], which makes the film a much stronger reflector than any optical component in the
So, a significant percentage of the light is reflected off the film, partly specular and partly diffuse. (For convenience, we will consider that paths
of the reflected light are the same and thus are already drawn for the incident light).
Thus, the blue arrows
indicate light reflected from the film. This light encounters the filter, which specularly reflects a
small fraction (red arrows
). The red rays are parallel and consequently focused onto a point on the film. (2)
The virtual source of the mirror point is traced by the dashed black lines. Note that the blue rays reflected by the film seem odd from the viewpoint
of specular reflection; they merely illustrate the fact that all light rays that originate from a single point on the film, and which are collected by
the lens, emerge parallel at the filter.
So, UFOs? No!