Editing Near-Earth object (section)

== Definitions ==
[[File:Potentially Hazardous Asteroids 2013.png|thumb|Plot of orbits of known [[Potentially hazardous object|potentially hazardous asteroids]] (size over {{convert|460|ft|m|order=flip|abbr=on}} and passing within {{convert|4.7|e6mi|e6km|order=flip|abbr=on}} of Earth's orbit) as of early 2013 ([[:File:PIA17041-Orbits-PotentiallyHazardousAsteroids-Early2013.jpg|alternate image]])]]

Near-Earth objects (NEOs) are formally defined by the [[International Astronomical Union]] (IAU) as all [[Small Solar System body|small Solar System bodies]] with orbits around the Sun that are at least partially closer than 1.3 [[astronomical unit]]s (AU; Sun–Earth distance) from the Sun.<ref name="IAU-NEOs"/> This definition excludes larger bodies such as [[planet]]s, like [[Venus]]; [[natural satellite]]s which orbit bodies other than the Sun, like Earth's [[Moon]]; and artificial bodies orbiting the Sun. A small Solar System body can be an [[asteroid]] or a [[comet]], thus an NEO is either a near-Earth asteroid (NEA) or a near-Earth comet (NEC). The organisations cataloging NEOs further limit their definition of NEO to objects with an orbital period under 200 years, a restriction that applies to comets in particular,<ref name="CNEOS-NEO-groups">{{cite web |title=NEO Basics. NEO Groups |publisher=NASA/JPL CNEOS |url=https://cneos.jpl.nasa.gov/about/neo_groups.html |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20250101153312/https://cneos.jpl.nasa.gov/about/neo_groups.html |archive-date=January 1, 2025}}</ref><ref name="NEOCC-DA">{{cite web |title=Definitions & Assumptions |publisher=[[European Space Agency|ESA]] [[Near-Earth Object Coordination Centre|NEOCC]] |url=https://neo.ssa.esa.int/definitions-assumptions |access-date=January 2, 2025 |url-status=live |archive-url=https://web.archive.org/web/20250101040757/https://neo.ssa.esa.int/definitions-assumptions |archive-date=January 1, 2025}}</ref> but this approach is not universal.<ref name="IAU-NEOs"/> Some authors further restrict the definition to orbits that are at least partly further than 0.983 AU away from the Sun.<ref name="MorbidelliAstIII"/><ref>{{Cite journal |last1=Waszczak |first1=Adam |last2=Prince |first2=Thomas A. |last3=Laher |first3=Russ |last4=Masci |first4=Frank |last5=Bue |first5=Brian |last6=Rebbapragada |first6=Umaa |last7=Barlow |first7=Tom |last8=Jason Surace |last9=Helou |first9=George |display-authors=2 |date=2017 |title=Small Near-Earth Asteroids in the Palomar Transient Factory Survey: A Real-Time Streak-detection System |journal=[[Publications of the Astronomical Society of the Pacific]] |volume=129 |issue=973 |at=part 034402 |doi=10.1088/1538-3873/129/973/034402 |issn=1538-3873 |arxiv=1609.08018|bibcode=2017PASP..129c4402W |s2cid=43606524}}</ref> NEOs are thus not necessarily currently near the Earth, but they can potentially approach the Earth relatively closely. Many NEOs have complex orbits due to constant perturbation by the Earth's gravity, and some of them can temporarily change from an orbit around the Sun to one around the Earth, but the term is applied flexibly for these objects, too.<ref name="ST111230"/>

The orbits of some NEOs intersect that of the Earth, so they pose a collision danger.<ref name="CHAPMAN04">{{cite journal |first=Clark R. |last=Chapman |title=The hazard of near-Earth asteroid impacts on earth |journal=[[Earth and Planetary Science Letters]] |volume=222 |issue=1 |pages=1–15 |date=May 2004 |doi=10.1016/j.epsl.2004.03.004 |bibcode=2004E&PSL.222....1C}}</ref> These are considered [[potentially hazardous object]]s (PHOs) if their estimated diameter is above 140 meters. PHOs include potentially hazardous asteroids (PHAs).<ref name="MPC-PHA-list"/><ref>{{cite journal |last1=Perna |first1=D. |last2=Barucci |first2=M. A. |last3=Fulchignoni |first3=M. |title=The near-Earth objects and their potential threat to our planet |journal=[[The Astronomy and Astrophysics Review]] |date=2013 |volume=21 |issue=1 |pages=65 |doi=10.1007/s00159-013-0065-4|bibcode=2013A&ARv..21...65P}}</ref> PHAs are defined based on two parameters relating to respectively their potential to approach the Earth dangerously closely and the estimated consequences that an impact would have if it occurs.<ref name="CNEOS-NEO-groups"/> Objects with both an Earth [[minimum orbit intersection distance]] (MOID) of 0.05&nbsp;AU or less and an [[Absolute magnitude#Solar System bodies (H)|absolute magnitude]] of 22.0 or brighter (a rough indicator of large size) are considered PHAs. Objects that either cannot approach closer to the Earth than {{convert |0.05 |AU |km mi |abbr=on |lk=in}}, or which are fainter than H = 22.0 (about {{convert|140|m|ft|abbr=on|lk=off}} in diameter with assumed [[albedo]] of 14%), are not considered PHAs.<ref name="CNEOS-NEO-groups"/>