A Streak of Light
On the night of the Deep Impact event, many hundreds of images were taken of comet Tempel 1 at the Kitt Peak Visitor Center Observatory. In the almost two hours of time that elapsed during that imaging, the comet's position changed against the background stars. When all of the images of this motion are added together, the resulting streak of light is shown in the image above. Starting from the left, the comet was its natural brightness. The streak brightens significantly in the middle, immediately after impact of the probe!
CREDIT: Kitt Peak Visitor's Center Observatory