Asteroid 1989 PB was discovered on August 9, 1989, by
on photographic plates taken on Palomar
Observatory's 18-inch Schmidt telescope.
The slightly elongated smudge near the center of this image is the asteroid.
Two days later, orbital calculations showed that this object was approaching the Earth and would pass within the Arecibo Observatory's field of view during August 19-22 at distances likely to provide echoes much stronger than in previous asteroid radar observations.