From Humanists Of Utah:
In 1989 both Voyager spacecraft had passed Neptune and Pluto. Carl Sagan wanted one last picture of Earth from “a hundred thousand times” as far away than the famous shots of Earth taken by astronauts from the moon during the Apollo series.
The result is stunning. In Sagan’s words, “Because of the reflection of sunlight off the spacecraft, the Earth seems to be sitting in a beam of light, as if there were some special significance to this small world. But it’s just an accident of geometry and optics. The Sun emits its radiation equitably in all directions. Had the picture been taken a little earlier or a little later there would have been no sunbeam highlighting the Earth.