It's the discovery of the first KBO!!! (Kuiper Belt Object)
The astronomer Dave Jewitt and his graduate student Jane Luu were looking for trans-Neptunian objects.
They were trying to find a faint asteroid among thousands of stars.
To accomplish this, they took many images of the same portion of the sky.
The stars stayed in the same location, but the asteroid slowly moved.
Voila! In 1992 they found the first KBO (now called 1992 QB1).
Now isn't that awesome?