PTF images of the near-Earth asteroid designated 2009 HK73. Three 60-second exposures (in g-band) separated by 10-minute intervals have been colorized red, green and blue, respectively, and stacked with respect to the stationary stars. The asteroid is seen as three colinear colored streaks. Most asteroids seen in PTF (e.g. main-belt asteroids) do not move fast enough to form a streak on individual exposures.