54509 YORP (2000 PH5) is an Apollo Near-Earth Object (NEO) discovered on August 3, 2000 by the Lincoln Laboratory Near-Earth Asteroid Research (LINEAR) Team at Socorro. Measurements of the rotation rate of this object provided the first observational evidence of the YORP effect, hence the name of the asteroid.
The asteroid is an Earth coorbital object, or quasi-satellite.
Observing the Spin-Up of an Asteroid For the very first time, astronomers have witnessed the speeding up of an asteroid's rotation, and have shown that it is due to a theoretical effect predicted but never seen before. The international team of scientists used an armada of telescopes to discover that the asteroid's rotation period currently decreases by 1 millisecond every year, as a consequence of the heating of the asteroid's surface by the Sun. Eventually it may spin faster than any known asteroid in the solar system and even break apart.
The minor planet 2000 PH5 is a very interesting object for the study of peculiar dynamical phenomena. We have shown that 2000 PH5 is in a Sun-Earth horseshoe orbit with orbital parameters that may suggest an origin in the Earth-Moon system. D. Vokrouhlickı has suggested that 2000 PH5 may be an excellent candidate for detecting the evolution of asteroid spin states due to thermal reemission of sunlight (YORP effect)