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54509 YORP
	Radar image and 3D model of YORP
Discovery
Discovered by	LINEAR
Discovery site	Lincoln Lab's ETS
Discovery date	3 August 2000
Designations
MPC designation	(54509) YORP
Named after	YORP effect
Alternative designations	2000 PH5
Minor planet category	Apollo ; NEO
Orbital characteristics
	Epoch 20 March 2003 (JD 2452718.5)
	Uncertainty parameter 0
Observation arc	1826 days (5.00 yr)
Aphelion	1.22998 AU (184.002 Gm)
Perihelion	0.77013 AU (115.210 Gm)
Semi-major axis	1.00005 AU (149.605 Gm)
Eccentricity	0.22991
Orbital period (sidereal)	1.00 yr (365.29 d)
Average orbital speed	29.31 km/s
Mean anomaly	314.13265°
Mean motion	0° 59m 7.901s / day
Inclination	1.83313°
Longitude of ascending node	281.88673°
Argument of perihelion	274.101°
Earth MOID	0.00268922 AU (402,302 km)
Jupiter MOID	3.72701 AU (557.553 Gm)
TJupiter	6.056
Physical characteristics
Dimensions	150×128×93 m
Synodic rotation period	0.2029 h (12.17 min)
Sidereal rotation period	0.2029 h; 12.174 min
Axial tilt	173°
Pole ecliptic latitude	−85°
Pole ecliptic longitude	180°
Geometric albedo	0.10?
Temperature	~278 K
Absolute magnitude (H)	22.7

54509 YORP (provisional designation 2000 PH₅) is an Earth co-orbital asteroid^[5] discovered on 3 August 2000 by the Lincoln Laboratory Near-Earth Asteroid Research (LINEAR) Team at Lincoln Laboratory Experimental Test Site in Socorro, New Mexico. 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's rate of rotation is increasing at the rate of (2.0 ± 0.2) × 10⁻⁴ deg/day² which between 2001 and 2005 caused the asteroid to rotate about 250° further than its spin rate in 2001 would have predicted.^[4] Simulations of the asteroid suggest that it may reach a rotation period of ~20 seconds near the end of its expected lifetime, which has a 75% probability of happening within the next 35 million years.^[6] The simulations also ruled out the possibility that close encounters with the Earth have been the cause of the increased spin rate.^[6]

On 2 January 2104, asteroid YORP will pass within 0.00530 AU (793,000 km; 493,000 mi) from Earth.^[7]

YORP is the largest member of a candidate asteroid family, another member of which is 2017 FZ2, that would have been formed through shedding of fragments of YORP or the breakup of a larger progenitor due to the YORP effect.^[8]