As scientists discover new asteroids, they add them to a map and highlight them white to indicate they are new ones. The final color of an asteroid indicates how closely it travels into the inner solar system: Earth Crossers are Red, Earth Approachers are Yellow, and all others are Green.
The time lapse covers the period from 1980 to 2010.
From szyzyg
Video created by Scott Manley.
source PopSci