Editing YORP effect (section)

== Observations ==
In 2007 there was direct observational confirmation of the YORP effect on the small asteroids [[54509 YORP]] (then designated {{mpl|2000 PH|5}})<ref name="LowryFitzsimmons2007">{{cite journal|last1=Lowry|first1=S. C.|last2=Fitzsimmons|first2=A.|last3=Pravec|first3=P.|last4=Vokrouhlicky|first4=D.|last5=Boehnhardt|first5=H.|last6=Taylor|first6=P. A.|last7=Margot|first7=J.-L.|last8=Galad|first8=A.|last9=Irwin|first9=M.|last10=Irwin|first10=J.|last11=Kusnirak|first11=P.|title=Direct Detection of the Asteroidal YORP Effect|journal=Science|volume=316|issue=5822|year=2007|pages=272–274|issn=0036-8075|doi=10.1126/science.1139040|bibcode=2007Sci...316..272L|pmid=17347414|s2cid=26687221 |url=https://pure.qub.ac.uk/portal/files/5430838/Science_2007_Lowry_272_4.pdf|access-date=2019-09-23|archive-date=2019-09-23|archive-url=https://web.archive.org/web/20190923110706/https://pure.qub.ac.uk/portal/files/5430838/Science_2007_Lowry_272_4.pdf|url-status=live}}</ref><ref name="TaylorMargot2007">{{cite journal|last1=Taylor|first1=P. A.|last2=Margot|first2=J.-L.|last3=Vokrouhlicky|first3=D.|last4=Scheeres|first4=D. J.|last5=Pravec|first5=P.|last6=Lowry|first6=S. C.|last7=Fitzsimmons|first7=A.|last8=Nolan|first8=M. C.|last9=Ostro|first9=S. J.|last10=Benner|first10=L. A. M.|last11=Giorgini|first11=J. D.|last12=Magri|first12=C.|title=Spin Rate of Asteroid (54509) 2000 PH5 Increasing Due to the YORP Effect|journal=Science|volume=316|issue=5822|year=2007|pages=274–277|issn=0036-8075|doi=10.1126/science.1139038|bibcode=2007Sci...316..274T|pmid=17347415|s2cid=29191700 |doi-access=free}}</ref> and [[1862 Apollo]].<ref>{{cite journal |author=Kaasalainen, Mikko |author2=Ďurech, Josef |author3=Warner, Brian D. |author4=Krugly, Yurij N. |author4-link=Yurij N. Krugly |author5=Gaftonyuk, Ninel M. | date = 2007 | title = Acceleration of the rotation of asteroid 1862 Apollo by radiation torques | journal = Nature | volume = 446 | issue = 7134 | pages = 420–422 | doi = 10.1038/nature05614 | bibcode=2007Natur.446..420K | pmid=17344861|s2cid=4420270 }}</ref> The spin rate of 54509 YORP will double in just 600,000 years, and the YORP effect can also alter the axial tilt and [[precession]] rate, so that the entire suite of YORP phenomena can send asteroids into interesting resonant spin states, and helps explain the existence of [[binary asteroid]]s.<ref>{{cite journal | last1 = Rubincam | first1 = D. P. | last2 = Paddack | first2 = S. J. | date = 2007 | title = As Tiny Worlds Turn | journal = Science | volume = 316 | issue = 5822 | pages = 211–212 | doi = 10.1126/science.1141930 | pmid = 17431161 | citeseerx = 10.1.1.205.5777 | s2cid = 118802966 }}</ref>

Observations show that asteroids larger than 125&nbsp;km in diameter have rotation rates that follow a [[Maxwell–Boltzmann distribution|Maxwellian frequency distribution]], while smaller asteroids (in the 50 to 125&nbsp;km size range) show a small excess of fast rotators. The smallest asteroids (size less than 50&nbsp;km) show a clear excess of very fast and slow rotators, and this becomes even more pronounced as smaller-sized populations are measured. These results suggest that one or more size-dependent mechanisms are depopulating the centre of the spin rate distribution in favour of the extremes. The YORP effect is a prime candidate. It is not capable of significantly modifying the spin rates of large asteroids by itself, so a different explanation must be sought for objects such as [[253 Mathilde]].

In late 2013 asteroid [[P/2013 R3]] was observed breaking apart, likely because of a high rotation speed from the YORP effect.<ref>{{cite web
|url=http://www.spacetelescope.org/news/heic1405/
|title=Hubble witnesses an asteroid mysteriously disintegrating
|access-date=2014-03-06
|archive-date=2014-03-12
|archive-url=https://web.archive.org/web/20140312045223/http://www.spacetelescope.org/news/heic1405/
|url-status=live
}}</ref>