View source for 2020 CD3

{{Short description|Temporary satellite of Earth}}
{{DISPLAYTITLE:{{mp|2020 CD|3}}}}
{{Use dmy dates|date=February 2020}}
{{Infobox planet
 | minorplanet     = yes
 | name            = {{mp|2020 CD|3}}
 | background      = #FFC2E0
 | image           = 2020 CD3 Gemini Color crop.jpg
 | image_scale      =
 | caption         = {{mp|2020 CD|3}} imaged in colour by [[Gemini North]]
 | discovery_ref   = &thinsp;<ref name="MPEC-2020-D104"/><ref name="MPC-object"/>
 | discoverer      = [[Mount Lemmon Survey|Mt. Lemmon Survey]]
  {{plainlist |
* [[Catalina Sky Survey#CSS/SSS team|Theodore A. Pruyne]]
* [[Kacper Wierzchoś|Kacper W. Wierzchoś]]&thinsp;<ref name="MPEC-2020-D104"/>
}}
 | discovery_site  = [[Mount Lemmon Observatory|Mt. Lemmon Obs.]] ([[Catalina Sky Survey|CSS]])
 | discovered      = 15 February 2020
 | mpc_name        = {{mp|2020 CD|3}}
 | alt_names       = C26FED2&thinsp;<ref name="NEO-Exchange"/><ref name="PseudoMPEC"/>
 | pronounced      = 
 | named_after     = 
 | mp_category     = {{nowrap|[[Near-Earth object|NEO]]{{·}}[[Arjuna asteroid|Arjuna]]&thinsp;<ref name="Marcos2020"/>{{·}}[[Apollo asteroid|Apollo]]&thinsp;<ref name="jpldata"/>}}<br />[[Temporary satellite|temporarily captured]]&thinsp;<ref name="MPEC-2020-D104"/>{{·}}[[co-orbital]]&thinsp;<ref name="Marcos2020"/>
 | orbit_ref       = &thinsp;<ref name="jpldata"/>
 | epoch           = 2022-Aug-09 ([[Julian day|JD]] 2459800.5)
 | uncertainty     = 0
 | observation_arc = 2.03 yr (742 days)
 | earliest_precovery_date = 9 May 2018
 | aphelion        = 1.0418 [[Astronomical unit|AU]]
 | perihelion      = 1.0162 AU
 | semimajor       = 1.029 AU
 | eccentricity    = 0.01245<br />(Geocentric [[Hyperbolic trajectory|hyperbolic]] e=58901)<ref name="geocentric"/>
 | period          = 1.04 yr (381.25 d)
 | mean_anomaly    = 151.09[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.94454818|sup=ms}} / day
 | inclination     = 0.63407°
 | asc_node        = 82.211°
 | arg_peri        = 49.972°
 | moid            = {{Convert|0.0212|AU|e6km LD|abbr=unit|lk=on}}
 | mean_diameter   = {{val|0.9|0.1|ul=m}} {{small|(albedo of 0.35)}}<ref name="Bolin2020"/><br/>{{val|1.2|0.1|ul=m}} {{small|(albedo of 0.23)}}<ref name="Bolin2020"/>
 | mass            = {{val|4900|ul=kg|p=~|fmt=commas}} {{small|(est.)}}<ref name="CNEOS"/>
 | density         = {{val|2.1|0.7|u=g/cm3}}<ref name="Bolin2020"/>
 | rotation        = {{val|1146.8|ul=s|fmt=commas}} or<br/>{{val|19.114|ul=min}} (double-peaked solution)<br />{{val|573.4|ul=s}} (single-peaked solution)<ref name="Bolin2020"/>
 | albedo          = 0.35 {{small|(assumed V-type)}}<ref name="Bolin2020"/><br/>0.23 {{small|(assumed from [[main belt asteroid|main belt]])}}
 | spectral_type   = [[V-type asteroid|V]]<ref name="Bolin2020"/><br/>[[Asteroid spectral types#Asteroid color indices|B–V]]={{val|0.90|0.07}}<ref name="Bolin2020"/><br/>V–R={{val|0.46|0.08}}<br/>R–I={{val|0.44|0.06}}
 | magnitude       = >30 {{small|(current)}}<ref name="NEODyS"/><br/>20 {{small|(at discovery)}}<ref name="MPC-object"/>
 | abs_magnitude   = {{val|31.80|0.34}}<ref name="jpldata"/><br/>31.8<ref name="MPC-object"/>
}}

'''{{mp|2020 CD|3}}''' (also '''CD3''' for short)<ref name="UT-20201124">{{cite news |last=Crewe |first=Ralph |title=Here's what we know about Earth's new minimoon |url=https://www.universetoday.com/148911/heres-what-we-know-about-earths-new-minimoon/ |date=24 November 2020 |work=[[Universe Today]] |access-date=25 November 2020 }}</ref><ref name="TAJ-20201123">{{cite journal |author=Fedorets, Grigori |display-authors=et al. |title=Establishing Earth's Minimoon Population through Characterization of Asteroid 2020 CD3 |date=23 November 2020 |journal=[[The Astronomical Journal]] |volume=160 |number=6 |page=277 |doi=10.3847/1538-3881/abc3bc |arxiv=2011.10380 |bibcode=2020AJ....160..277F |s2cid=227119071 |doi-access=free }}</ref> is a tiny [[near-Earth asteroid]] (or [[Claimed moons of Earth|minimoon]]) that ordinarily orbits the Sun but makes close approaches to the Earth–Moon system, in which it can temporarily enter [[Earth]] orbit through [[temporary satellite]] capture (TSC). It was discovered at the [[Mount Lemmon Observatory]] by astronomers Theodore Pruyne and [[Kacper Wierzchoś]] on 15 February 2020, as part of the [[Mount Lemmon Survey]] or [[Catalina Sky Survey]]. The asteroid's discovery was announced by the [[Minor Planet Center]] on 25 February 2020, after subsequent observations confirmed that it was orbiting Earth.

It is the second temporary satellite of Earth discovered ''[[in situ]]'', after {{mpl|2006 RH|120}}, which was discovered in 2006. Based on its nominal trajectory, {{mp|2020 CD|3}} was captured by Earth around 2016–2017, and escaped Earth's gravitational [[Sphere of influence (astrodynamics)|sphere of influence]] around 7 May 2020.<ref name="Marcos2020"/><ref name="Bolin2020"/><ref name="Horizons2020-May-07"/> {{mp|2020 CD|3}} will make another close pass to Earth in March 2044, though it will most likely not be captured by Earth due to the greater approach distance.<ref name="NEODyS-CA"/><ref name="Koren2020"/>

{{mp|2020 CD|3}} has an [[absolute magnitude]] around 32, indicating that it is very small in size. Assuming that {{mp|2020 CD|3}} has a low [[albedo]] characteristic of dark, [[Carbonaceous chondrite|carbonaceous]] [[C-type asteroid]]s, its diameter is probably around {{convert|1.9|-|3.5|m|ft|0}}.<ref name="Byrd2020"/><ref name="Crane2020"/> {{mp|2020 CD|3}} is classified as an [[Arjuna asteroid]], a subtype of small Earth-crossing [[Apollo asteroid]]s that have Earth-like orbits.<ref name="Marcos2020"/>

== Discovery ==
[[File:2020 CD3 Gemini Color.jpg|thumb|left|upright=1|Colour composite image of {{mp|2020 CD|3}} obtained by the [[Gemini Observatory]] on 24 February 2020<ref name="Gemini"/>]]

{{mp|2020 CD|3}} was discovered on 15 February 2020, by astronomers Theodore Pruyne and [[Kacper Wierzchoś]] at the Mount Lemmon Observatory. The discovery formed part of the Mount Lemmon Survey designed for discovering near-Earth objects, which is also part of the Catalina Sky Survey conducted at Tucson, Arizona.<ref name="MPEC-2020-D104"/><ref name="Gemini"/> {{mp|2020 CD|3}} was found as a faint, 20th magnitude object in the [[constellation (astronomy)|constellation]] of [[Virgo (constellation)|Virgo]], located about {{cvt|0.0019|AU|km mi|lk=in}} from Earth at the time.<ref name="NEODyS-Eph-Dis"/><ref name="King2020"/>{{efn|The [[celestial coordinates]] of {{mp|2020 CD|3}} at the time of discovery were {{RA|13|03|33.11}} {{Dec|+09|10|43.1}}.<ref name="MPEC-2020-D104"/> See [[Virgo (constellation)|Virgo]] for constellation coordinates.}} The observed orbital motion of the object suggested that it may be gravitationally bound to Earth, which prompted further observations to secure and determine its motion.<ref name="PseudoMPEC"/>

The object's discovery was reported to the [[Minor Planet Center]]'s [[Near-Earth Object Confirmation Page]] (NEOCP), where a preliminary orbit was calculated from additional observations conducted at several observatories.<ref name="PseudoMPEC"/> Follow-up observations of {{mp|2020 CD|3}} spanned six days since its discovery, and the object was formally announced in a [[Minor Planet Electronic Circular]] notice issued by the Minor Planet Center on 25 February 2020. No indication of [[perturbation (astronomy)|perturbation]]s by [[solar radiation pressure]] was observed, and {{mp|2020 CD|3}} could not be linked to any known artificial object.<ref name="MPEC-2020-D104"/> Although the evidence implied that {{mp|2020 CD|3}} is most likely a dense, rocky asteroid, the possibility of the object being an artificial object, such as a dead satellite or rocket booster, had not yet been fully ruled out.<ref name="Howell2020"/><ref name="King2020"/>

[[Precovery]] images of {{mp|2020 CD|3}} have been identified back to May 2018.<ref name="MPC-object"/>

== Nomenclature ==
Upon discovery, the asteroid was given the temporary internal designation C26FED2.<ref name="PseudoMPEC"/><ref name="NEO-Exchange"/> After follow up observations confirming the object, it was then given the [[Minor planet provisional designation|provisional designation]] {{mp|2020 CD|3}} by the Minor Planet Center on 25 February 2020.<ref name="MPEC-2020-D104"/> The provisional designation signifies the object's discovery date and year. The object has not yet been issued a permanent [[minor planet number]] by the Minor Planet Center due to its modest [[observation arc]] of a couple years and that it has not been observed at enough [[Opposition (astronomy)|oppositions]].<ref name="Nomenclature"/>

== Orbit ==
[[File:Animation of 2020 CD3's orbit around Earth.gif|thumb|Animation of {{mp|2020 CD|3}}'s orbit around Earth<br />{{legend2|Magenta|{{mp|2020 CD|3}}}}{{·}}{{legend2|DarkKhaki|Moon}}{{·}}{{legend2|RoyalBlue|Earth}}]]
Prior to the temporary capture of {{mp|2020 CD|3}}, its heliocentric orbit was probably Earth-crossing, either falling into the categories of an [[Aten asteroid|Aten-type]] orbit ([[semi-major axis|a]]&thinsp;<&thinsp;1&nbsp;AU) or an [[Apollo asteroid|Apollo-type]] orbit ([[semi-major axis|a]]&thinsp;>&thinsp;1&nbsp;AU), with the former considered to be more likely.<ref name="Marcos2020"/>

=== Temporary capture ===
[[File:2020CD3.jpg|thumb|The orbit of {{mp|2020 CD|3}} around the Earth. The white band is the orbit of the Moon.]]
[[File:2020CD3 earth-minimoon-orbits-2015-2020.gif|thumb|Trajectory and orbits of {{mp|2020 CD|3}} around Earth, from 2015 to 2020{{efn|JPL Horizons 28 Feb 2020 solution<ref name="jpldata"/>}}]]

Because {{mp|2020 CD|3}} has an Earth-like heliocentric orbit, its motion relative to Earth is low, allowing for it to slowly approach the planet and be captured.<ref name="Marcos2020"/> Nominal orbit solutions for {{mp|2020 CD|3}} suggest that it was captured by Earth between 2016 and 2017, and left [[geocentric]] orbit by May 2020 according to simulations of its orbit.<ref name="Marcos2020"/><ref name="Bolin2020"/> The geocentric orbit of {{mp|2020 CD|3}} is [[Chaos theory|chaotic]] due to the combined effects of [[tidal forces]] from the Sun and Earth as well as repeated close encounters with the Moon.<ref name="Plait2020"/><ref name="Howell2020"/> The Moon gravitationally perturbs {{mp|2020 CD|3}}'s geocentric orbit, causing it to be unstable. Over the course of {{mp|2020 CD|3}}'s orbit around Earth, repeated close encounters with the Moon leads to ejection from its geocentric orbit as the Moon's perturbations can transfer enough [[momentum]] for {{mp|2020 CD|3}} to escape Earth's gravitational influence.<ref name="Baoyin2010"/><ref name="Plait2020"/><ref name="Naidu2020"/>

{{mp|2020 CD|3}}'s orbit around Earth is highly variable and eccentric, hence predictions of its past trajectory before mid-2017 are uncertain.<ref name="Crane2020"/><ref name="Naidu2020"/> Due to the [[Yarkovsky effect]] on small asteroids, the first precovery image being from 2018, and numerous approaches to the Earth and Moon, it is unknown if the asteroid was closer than the Moon on Christmas Day 2015.<ref name="Christmas2015"/>

{| class="wikitable" style="font-size: 0.9em;"
|+Earth approach Christmas Day 2015?<ref name="Christmas2015"/>
! Date
! [[JPL Horizons]]<br />[[Curve fitting|nominal]] geocentric<br />distance ([[astronomical unit|AU]])
! [[NEODyS]]<br />nominal geocentric<br />distance (AU)
! Find_Orb<br />nominal geocentric<br />distance (AU)
! [[ESA]] NEOCC<br />nominal geocentric<br />distance (AU)
! [[Minor Planet Center|MPC]]<br />nominal geocentric<br />distance (AU)
|-
|2015-Dec-25 ||{{Convert|0.0006|AU|e3km|abbr=unit|lk=on}} ||{{Convert|0.0162|AU|e6km|abbr=unit}} ||{{Convert|0.288|AU|e6km|abbr=unit}} ||{{Convert|0.345|AU|e6km|abbr=unit}} ||{{Convert|0.834|AU|e6km|abbr=unit|lk=on}}
|}

Between September 2017 and February 2020 it made 12 close approaches to Earth,<ref name="NEODyS-CA"/> during which time it was never more than {{Convert|0.0112|AU|e6km|abbr=unit|lk=on}} from Earth.<ref name="Horizons2017-2020"/> According to the [[JPL Small-Body Database]], on 15 September 2017 it passed {{convert|12000|km|mi|abbr=unit}} from the Moon.<ref name="jpldata"/> The closest approach to Earth occurred on 4 April 2019, when it approached to a distance of {{convert|13104|km|mi|abbr=unit}}.<ref name="jpldata"/>{{efn|{{value|13104|u=km}} – Earth radius of {{val|6371|u=km}} is {{val|6733|u=km}} from the surface of Earth.}} The final close approach in 2020 occurred on 13 February 2020 at a distance of about {{cvt|41000|km|mi}} from Earth's surface.<ref name="Naidu2020"/> The orbital period of {{mp|2020 CD|3}} around Earth ranged from 70 to 90 days.<ref name="Naidu2020"/> {{mp|2020 CD|3}} escaped Earth's [[Hill sphere]] at roughly {{Convert|0.01|AU|e6km|abbr=unit|lk=on}} in March 2020<ref name="Naidu2020"/><ref name="Horizons-Hill"/> and returned to solar orbit on 7 May 2020.<ref name="Marcos2020"/>

{| class="wikitable" style="text-align:center; font-size: 0.9em;"
|+Escaping geocentric orbit 7 May 2020{{efn|name=hill|Already outside of the Earth's [[Hill sphere]] which has a radius of roughly {{convert|0.01|AU|e6km|abbr=unit}}.}}<br/>(assuming the Earth+asteroid are the only objects in the Solar System)
! [[Epoch (astronomy)|Epoch]]
! Earth distance<ref name="Horizons-Hill"/>
! Geocentric<br/>[[Orbital eccentricity|eccentricity]]<ref name="Horizons2020-May-07"/>
! [[Apsis|Apogee]]<ref name="Horizons2020-May-07"/>
! [[Orbital period]]<ref name="Horizons2020-May-07"/>
|-
|2020-May-07 || {{Convert|0.0189|AU|e6km|abbr=unit|lk=on}} ||0.9901 ||{{Convert|2.25|AU|e6km|abbr=unit}} ||{{Convert|253341|day|year||order=flip}}
|-
|2020-May-08 || {{Convert|0.0191|AU|e6km|abbr=unit}} ||1.0347 ||<math>\infty</math> ||<math>\infty</math>
|}

Being captured into a temporary orbit around Earth, {{mp|2020 CD|3}} is a temporarily captured object or a [[temporary satellite]] of Earth.<ref name="MPEC-2020-D104"/><ref name="Gough2020"/> {{mp|2020 CD|3}} has also been widely referred to in the media as a "mini-moon" of Earth, due to its small size.<ref name="Gemini"/><ref name="Byrd2020"/><ref name="Crane2020"/><ref name="Boyle2020"/> {{mp|2020 CD|3}} is the second known temporary captured object discovered ''in situ'' around Earth, with the first being {{mpl|2006 RH|120}} discovered in 2006.<ref name="Boyle2020"/> Other objects have also been suspected to have once been temporarily captured, including the small near-Earth asteroid [[1991 VG]] and the [[bolide]] [[DN160822 03]].<ref name="Tancredi1997"/><ref name="Gohd2019"/> Objects that get temporarily captured by Earth are thought to be common, though larger objects over {{cvt|2|ft|m|order=flip|sigfig=1}} in diameter are believed to be less likely to be captured by Earth and detected by modern telescopes.<ref name="Boyle2020"/>

=== Future approaches ===
{{mp|2020 CD|3}} will continue orbiting the Sun and will approach Earth on 20 March 2044, from a distance of {{convert|0.0245|AU|e6km e6mi|abbr=unit}}.<ref name="NEODyS-CA"/> It is unlikely that {{mp|2020 CD|3}} will be captured by Earth in the March 2044 encounter, as the approach distance is too large for capture<ref name="Koren2020"/> and outside of Earth's [[Hill sphere]]. The next encounter will be August 2061, when it is expected to approach Earth from a nominal distance of {{convert|0.034|AU|e6km e6mi|abbr=unit}}.<ref name="NEODyS-CA"/> After the 2061 encounter the uncertainties in future encounters become much greater. By 2082 close approaches have a [[3-sigma]] uncertainty of {{no wrap|±7 days.}}<ref name=jpldata/>

The possibility of {{mp|2020 CD|3}} [[impact event|impacting]] Earth has been considered by the [[Jet Propulsion Laboratory]]'s [[Sentry (monitoring system)|Sentry risk table]].<ref name="CNEOS"/> JPL's solution accounts for non-gravitational forces<ref name="jpldata"/> as the multi-decade motion of a very small object is greatly affected by [[Yarkovsky effect|solar heating]]. Being only a few meters in size, an impact by {{mp|2020 CD|3}} would pose no threat to Earth as it would most likely fragment and disintegrate upon [[atmospheric entry]].<ref name="King2020"/> With a cumulative impact probability of 2.5%,<ref name="CNEOS"/> it is listed as the most likely object to impact Earth, but because of the harmless size of {{mp|2020 CD|3}}, it is given a [[Torino Scale]] rating of 0 and a cumulative [[Palermo Scale]] rating of –5.20<ref name="CNEOS"/> Within the next 100 years, the date with the highest probability of impact is 9 September 2082, which is estimated to have an impact probability of 0.85% and a negligible Palermo Scale rating of –5.66.<ref name="CNEOS"/> [[JPL Horizons On-Line Ephemeris System|JPL Horizon]]'s nominal orbit has the asteroid passing {{Convert|0.00251|AU|e3km|abbr=unit|lk=on}} from Earth on 8 October 2082 (29 days after the virtual impactor).<ref name="Horizons2082-CA"/>

== Physical characteristics ==
{{update section|date=August 2020}}
{{mp|2020 CD|3}} is estimated to have an [[Absolute magnitude#Solar System bodies (H)|absolute magnitude (H)]] around 31.7, indicating that it is very small in size.<ref name="jpldata"/> Studies reported in November 2020 have determined that the asteroid is about {{convert|1-2|m|ft|abbr=on}} in diameter.<ref name="UT-20201124" /><ref name="TAJ-20201123" /> The rotation period and [[albedo]] of {{mp|2020 CD|3}} have not been measured due to the limited number of observations.<ref name="Howell2020"/> Assuming that the albedo of {{mp|2020 CD|3}} is similar to those of dark, [[carbonaceous]] [[C-type asteroids]], the diameter of {{mp|2020 CD|3}} is around {{cvt|1.9|-|3.5|m|ft|0}}, comparable to in size to that of a small [[car]].<ref name="Crane2020"/><ref name="Gough2020"/> The [[Sentry (monitoring system)#Sentry Risk Table|JPL Sentry risk table]] estimates {{mp|2020 CD|3}} to have a mass of {{cvt|4900|kg|lb}}, based on the assumption that the asteroid has a diameter of {{cvt|2|m|ft}}.<ref name="CNEOS"/>

== See also ==
* {{mpl|1991 VG}} – near-Earth asteroid temporarily captured by Earth after its discovery in 1991
* {{mpl|2006 RH|120}} – the first temporary Earth satellite discovered ''in situ'' 2006
* {{mpl|2022 NX|1}} another temporary Earth satellite discovered in 2022
* {{mpl|2023 FY|3}}{{Snd}} another temporary Earth satellite discovered in 2023
* [[Claimed moons of Earth]]
* [[Quasi-satellite]]

== Notes ==
{{notelist}}

== References ==
{{reflist|refs=
<ref name="jpldata">{{cite web
  |type       = 2020-03-22 last obs.
  |title      = JPL Small-Body Database Browser: 2020 CD3
  |url        = https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=2020CD3&view=OPC
  |publisher  = [[Jet Propulsion Laboratory]]
  |access-date = 25 February 2020}}</ref>

<ref name="MPC-object">{{cite web
  |title      = 2020 CD3
  |work       = Minor Planet Center
  |publisher  = International Astronomical Union
  |url        = http://www.minorplanetcenter.net/db_search/show_object?object_id=2020+CD3
  |access-date = 25 February 2020}}</ref>

<ref name="NEODyS">{{cite web
  |title       = 2020CD3
  |url         = https://newton.spacedys.com/neodys/index.php?n=2020cd3&pc=1.1.0
  |work        = Near Earth Objects – Dynamic Site
  |publisher   = Department of Mathematics, University of Pisa, Italy
  |access-date  = 25 February 2020}}</ref>

<ref name="NEODyS-CA">{{cite web
  |title       = 2020CD3 Close Approaches
  |url         = https://newton.spacedys.com/neodys/index.php?pc=1.1.8&n=2020cd3
  |work        = Near Earth Objects – Dynamic Site
  |publisher   = Department of Mathematics, University of Pisa, Italy
  |archive-url = https://web.archive.org/web/20211023114234/https://newton.spacedys.com/neodys/index.php?pc=1.1.8&n=2020cd3
  |archive-date= 2021-10-23
  |url-status=live
  |access-date  = 1 March 2020}}</ref>

<ref name="NEODyS-Eph-Dis">{{cite web
  |type       = Ephemerides at discovery
  |title      = 2020 CD3 Ephemerides
  |url        = https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=2020CD3&oc=500&y0=2020&m0=2&d0=15&h0=10&mi0=00&y1=2020&m1=2&d1=16&h1=10&mi1=56&ti=1.0&tiu=minutes
  |work       = Near Earth Objects – Dynamic Site
  |publisher  = Department of Mathematics, University of Pisa, Italy
  |access-date = 28 February 2020}}</ref>

<ref name="NEO-Exchange">{{cite web
  |title      = 2020 CD3
  |url        = https://neoexchange.lco.global/target/56705/
  |work       = NEO Exchange
  |publisher  = [[Las Cumbres Observatory]]
  |date       = 15 February 2020
  |access-date = 25 February 2020}}</ref>

<ref name="PseudoMPEC">{{cite web
 |title        = "Pseudo-MPEC" for C26FED2
 |url          = https://www.projectpluto.com/neocp2/mpecs/C26FED2.htm
 |publisher    = Project Pluto
 |date         = 24 February 2020
 |access-date  = 25 February 2020
 |archive-date = 25 February 2020
 |archive-url  = https://web.archive.org/web/20200225081347/https://www.projectpluto.com/neocp2/mpecs/C26FED2.htm
 |url-status   = dead
}}</ref>

<!-- prior to discovery -->
<ref name="Nomenclature">{{cite web
  |title      = How Are Minor Planets Named?
  |url        = https://minorplanetcenter.net/iau/info/HowNamed.html
  |work       = Minor Planet Center
  |publisher  = International Astronomical Union
  |access-date = 29 February 2020}}</ref>

<ref name="Tancredi1997">{{cite journal
  |title      = An Asteroid in a [sic] Earth-like Orbit
  |last       = Tancredi |first = G.
  |date       = September 1997
  |journal    = [[Celestial Mechanics and Dynamical Astronomy]]
  |volume     = 69
  |issue      = 1/2
  |pages      = 119–132
  |doi        = 10.1023/A:1008378316299
  |bibcode    = 1997CeMDA..69..119T|s2cid = 189823446 }}</ref>

<ref name="Baoyin2010">{{cite journal
  |title      = Capturing Near Earth Objects
  |last1      = Baoyin |first1 = He-Xi
  |last2      = Chen |first2 = Chen
  |last3      = Li |first3 = Jun-Feng
  |date       = June 2010
  |journal    = Research in Astronomy and Astrophysics
  |volume     = 10
  |issue      = 6
  |pages      = 587–598
  |doi        = 10.1088/1674-4527/10/6/008
  |arxiv      = 1108.4767
  |bibcode    = 2010RAA....10..587B|s2cid = 119251954 }}</ref>

<ref name="Gohd2019">{{cite news
  |title      = Scientists Spot Rare Minimoon Fireball Over Australia
  |url        = https://www.space.com/minimoon-fireball-over-australia-desert.html
  |last       = Gohd |first = Chelsea
  |website    = Space.com
  |date       = 2 December 2019
  |access-date = 29 February 2020}}</ref>

<!-- after discovery -->
<ref name="MPEC-2020-D104">{{cite web
  |title      = MPEC 2020-D104 : 2020 CD3: Temporarily Captured Object
  |url        = https://minorplanetcenter.net/mpec/K20/K20DA4.html
  |work       = Minor Planet Electronic Circular
  |publisher  = [[Minor Planet Center]]
  |date       = 25 February 2020
  |access-date = 25 February 2020}}</ref>

<ref name="Byrd2020">{{cite news
  |title      = <!-- Looks like Earth has a new natural moon -->New image of Earth’s new mini-moon
  |url        = https://earthsky.org/space/new-natural-temporary-moon-for-earth-2020-cd3
  |last       = Byrd |first = Deborah 
  |work       = EarthSky
  |date       = 26 February 2020
  |access-date = 26 February 2020}}</ref>

<ref name="Crane2020">{{cite news
  |title      = Earth has acquired a brand new moon that's about the size of a car
  |url        = https://www.newscientist.com/article/2235427-earth-has-acquired-a-brand-new-moon-thats-about-the-size-of-a-car/
  |last       = Crane |first = Leah
  |work       = New Scientist
  |date       = 26 February 2020
  |access-date = 27 February 2020}}</ref>

<ref name="Naidu2020">{{cite news
  |title      = Tiny Object Discovered in Distant Orbit Around the Earth
  |url        = https://cneos.jpl.nasa.gov/news/news205.html
  |last1      = Naidu |first1 = Shantanu
  |last2      = Farnocchia |first2 = Davide
  |work       = Center for Near Earth Object Studies
  |publisher  = Jet Propulsion Laboratory
  |access-date = 3 March 2020}}</ref>

<ref name="Boyle2020">{{cite news
  |title      = A New Mini-Moon Was Found Orbiting Earth. There Will Be More.
  |url        = https://www.nytimes.com/2020/02/27/science/mini-moon-earth.html
  |last       = Boyle |first = Rebecca
  |work       = The New York Times
  |date       = 27 February 2020
  |access-date = 29 February 2020}}</ref>

<ref name="Gough2020">{{cite web
  |title      = Astronomers Discover a Tiny New Temporary Moon for the Earth. Welcome to the Family 2020 CD3
  |url        = https://www.universetoday.com/145157/astronomers-discover-a-tiny-new-temporary-moon-for-the-earth-welcome-to-the-family-2020-cd3/
  |last       = Gough |first = Evan
  |work       = Universe Today
  |date       = 27 February 2020
  |access-date = 29 February 2020}}</ref>

<ref name="Plait2020">{{cite web
  |title      = The Earth has a new minimoon! But not for long...
  |url        = https://www.syfy.com/syfywire/the-earth-has-a-new-minimoon-but-not-for-long
  |last       = Plait |first = Phil
  |author-link = Phil Plait
  |work       = Bad Astronomy
  |publisher  = Syfy Wire
  |date       = 27 February 2020
  |access-date = 29 February 2020}}</ref>

<ref name="Gemini">{{cite press release
  |title      = Gemini Telescope Images "Minimoon" Orbiting Earth — in Color!
  |url        = https://nationalastro.org/news/gemini-telescope-images-minimoon-orbiting-earth-in-color/
  |work       = National Optical-Infrared Astronomy Research Laboratory
  |publisher  = [[National Science Foundation]]
  |date       = 27 February 2020
  |access-date = 28 February 2020}}</ref>

<ref name="Howell2020">{{cite web
  |title      = How scientists found Earth's new minimoon and why it won't stay here forever
  |url        = https://www.space.com/minimoon-2020-cd3-discovery-around-earth-explained.html
  |last       = Howell |first = Elizabeth
  |website    = Space.com
  |date       = 28 February 2020
  |access-date = 29 February 2020}}</ref>

<ref name="King2020">{{cite web
  |title      = Earth Has A Mini-Moon — But Not for Long!
  |url        = https://skyandtelescope.org/astronomy-news/observing-news/earths-mini-moon/
  |last       = King |first = Bob
  |work       = Sky & Telescope
  |date       = 2 March 2020
  |access-date = 3 March 2020}}</ref>

<ref name="CNEOS">{{cite web
  |title      = 2020 CD3 -- Earth Impact Risk Summary
  |url        = https://cneos.jpl.nasa.gov/sentry/details.html#?des=2020%20CD3
  |work       = Center for Near Earth Object Studies
  |publisher  = Jet Propulsion Laboratory
  |access-date = 3 March 2020}}</ref>

<ref name="Koren2020">{{cite news
  |title      = A Fleeting Moment in the Solar System
  |url        = https://www.theatlantic.com/science/archive/2020/03/mini-moon-earth-lost/608455/
  |first      = Marina |last = Koren
  |work       = [[The Atlantic]]
  |date       = 20 March 2020
  |access-date = 2 April 2020}}</ref>

<ref name="Marcos2020">{{cite journal
  |title      = On the orbital evolution of meteoroid 2020 CD3, a temporarily captured orbiter of the Earth-Moon system
  |url        = https://academic.oup.com/mnras/article-abstract/494/1/1089/5811202
  |first1     = Carlos |last1 = de la Fuente Marcos
  |first2     = Raúl |last2 = de la Fuente Marcos
  |date       = 7 April 2020 
  |journal    = [[Monthly Notices of the Royal Astronomical Society]] 
  |volume     = 494
  |issue      = 1
  |pages      = 1089–1094
  |doi        = 10.1093/mnras/staa809
  |doi-access = free
 |arxiv      = 2003.09220
  |bibcode    = 2020MNRAS.494.1089D|s2cid = 214605877
 }}</ref>

<ref name="Bolin2020">{{cite journal
  |display-authors = etal
  |first1     = Bryce T. |last1 = Bolin
  |first2     = Christoffer |last2 = Fremling
  |first3     = Timothy R. |last3 = Holt
  |first4     = Matthew J. |last4 = Hankins
  |first5     = Tomás |last5 = Ahumada
  |first6     = Shreya |last6 = Anand
  |date       = August 2020
  |title      = Characterization of Temporarily-Captured Minimoon 2020 CD<sub>3</sub> by Keck Time-resolved Spectrophotometry
  |journal = The Astrophysical Journal |volume = 900 |issue = 2 |pages = L45 |doi = 10.3847/2041-8213/abae69 |arxiv     = 2008.05384
  |bibcode = 2020ApJ...900L..45B |s2cid = 221103592 |doi-access = free }}</ref>

<!-- Ephemeris -->
<ref name="Horizons2017-2020">{{cite web
  |title=Horizons Batch for September 2017 – April 2020 Geocentric distance
  |type=Maximum Apogee occurs 2020-Jan-05 @ 0.011179 (1.7 million km)
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272017-Sep-18%27&STOP_TIME=%272020-Apr-02%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720%27
  |archive-url=https://web.archive.org/web/20220711231105/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272017-Sep-18%27&STOP_TIME=%272020-Apr-02%27&STEP_SIZE=%271+day%27&QUANTITIES=%2720%27
  |archive-date=2022-07-11
  |url-status=live
  |accessdate=2022-07-11}} (JPL#27/Soln.date: 2021-Jun-25) ([https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=2020CD3&oc=500&y0=2020&m0=1&d0=5&y1=2020&m1=1&d1=5&ti=1.0&tiu=days NEODyS-2 for 5 Jan 2020])</ref>

<ref name="Horizons-Hill">{{cite web
  |title=Horizons Batch for March 2020 – May 2020 Geocentric distance
  |type=Escaping Earth's Hill Sphere @ ~0.01au
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272020-Mar-01%27&STOP_TIME=%272020-May-08%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720%27
  |archive-url=https://web.archive.org/web/20220708154827/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272020-Mar-01%27&STOP_TIME=%272020-May-08%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720%27
  |archive-date=2022-07-08
  |url-status=live
  |accessdate=2022-07-07}} (JPL#27/Soln.date: 2021-Jun-25)</ref>

<ref name="Horizons2020-May-07">{{cite web
  |title       = JPL Horizons On-Line Ephemeris for 2020 CD3 orbit of Earth (geocentric) at epoch 2020-May-07
  |work        = [[JPL Horizons On-Line Ephemeris System]]
  |publisher   = [[Jet Propulsion Laboratory]]
  |url         = https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%272020-May-01%27&STOP_TIME=%272020-May-14%27&STEP_SIZE=%271%20day%27&CENTER=%27@399%27&OUT_UNITS=%27AU-D%27
  |archive-url=https://web.archive.org/web/20220708160822/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%272020-May-01%27&STOP_TIME=%272020-May-14%27&STEP_SIZE=%271%20day%27&CENTER=%27@399%27&OUT_UNITS=%27AU-D%27
  |archive-date=2022-07-08
  |url-status=live
  |access-date = 2022-07-08}} Geocentric solution. Ephemeris Type: Orbital Elements / Center: @399</ref>

<ref name="Horizons2082-CA">{{cite web
  |title=Horizons Batch for September 2082 – November 2082 Geocentric distance
  |type=Earth approach occurs 2082-Oct-08 06:47 @ 0.002507 AU
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272082-Sep-01%27&STOP_TIME=%272082-Nov-19%27&STEP_SIZE=%271%20day%27&QUANTITIES=%2720%27
  |accessdate=2022-07-10}} (JPL#27/Soln.date: 2021-Jun-25)</ref>

<ref name="Christmas2015">{{cite web
  |title=Horizons Batch for Christmas 2015 Geocentric distance
  |type=Nominal is 0.0006 AU (90,000km)
  |publisher=[[JPL Horizons On-Line Ephemeris System|JPL Horizons]]
  |url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272015-Dec-25%27&STOP_TIME=%272015-Dec-26%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720%27
  |archive-url=https://web.archive.org/web/20220714064045/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&START_TIME=%272015-Dec-25%27&STOP_TIME=%272015-Dec-26%27&STEP_SIZE=%272+days%27&QUANTITIES=%2720%27
  |archive-date=2022-07-14
  |url-status=live
  |accessdate=2022-07-13}} (JPL#27/Soln.date: 2021-Jun-25) ([https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=2020CD3&oc=500&y0=2015&m0=12&d0=25&y1=2015&m1=12&d1=25&ti=1.0&tiu=days NEODyS-2 on 25 Dec 2015]) ([https://www.projectpluto.com/cgi-bin/fo/fo_serve.cgi?obj_name=2020+CD3&year=2015-12-25&n_steps=1&stepsize=1 Find_Orb on 25 Dec 2015]) ([http://neo.ssa.esa.int/o/PSDB-portlet/ephemerides?des=2020CD3&oc=500&t0=2015-12-25T00:00Z&t1=2015-12-25T01:00Z&ti=1&tiu=days ESA NEOCC on 25 Dec 2015])</ref>

<ref name="geocentric">{{cite web
  |title       = JPL Horizons On-Line Ephemeris for 2020 CD3 orbit of Earth (geocentric) at epoch 2022-Aug-09
  |url         = https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%272020+CD3%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%272022-Aug-09%27&STOP_TIME=%272100-01-01%27&STEP_SIZE=%27100%20years%27&CENTER=%27@399%27&OUT_UNITS=%27AU-D%27
  |work        = [[JPL Horizons On-Line Ephemeris System]]
  |publisher   = [[Jet Propulsion Laboratory]]
  |access-date = 21 August 2022}} Geocentric solution. Ephemeris Type: Orbital Elements / Center: @399 / Time Span: 2022-Aug-09 (to match infobox epoch)</ref>

}} <!-- end of reflist -->

== External links ==
{{Commons category}}
* [https://skyandtelescope.org/astronomy-news/observing-news/earths-mini-moon/ Earth Has A Mini-Moon — But Not for Long!] by Bob King, ''[[Sky & Telescope]]'', 2 March 2020
* [https://www.nytimes.com/2020/02/27/science/mini-moon-earth.html A New Mini-Moon Was Found Orbiting Earth. There Will Be More.] by Rebecca Boyle, ''[[The New York Times]]'', 27 Feb 2020
* [https://nationalastro.org/news/gemini-telescope-images-minimoon-orbiting-earth-in-color/ Gemini Telescope Images "Minimoon" Orbiting Earth — in Color!] {{Webarchive|url=https://web.archive.org/web/20200810205605/https://www.nationalastro.org/news/gemini-telescope-images-minimoon-orbiting-earth-in-color/ |date=10 August 2020 }}, OIR Laboratory press release, 27 Feb 2020
* [https://earthsky.org/space/new-natural-temporary-moon-for-earth-2020-cd3 Looks like Earth has a new natural moon] by Deborah Byrd, ''EarthSky'', 26 Feb 2020
* [https://minorplanetcenter.net/mpec/K20/K20DA4.html MPEC 2020-D104 : 2020 CD3: Temporarily Captured Object], [[Minor Planet Center]] announcement, 25 Feb 2020
* {{NeoDys|2020cd3}}
* {{JPL small body}}

{{2020 in space|state=collapsed}}
<!--use upon numbering: {{Minor planets navigator | |number=? |PageName={{mp|(?) 2020 CD|3}} | }} -->
{{Portal bar|Astronomy|Outer Space}}
{{Authority control}}

{{DEFAULTSORT:2020 CD3}}
[[Category:Apollo asteroids|#]]
[[Category:Minor planet object articles (unnumbered)]]
[[Category:Near-Earth objects in 2020|20200215]]
[[Category:Astronomical objects discovered in 2020|20200215]]
[[Category:Earth co-orbital asteroids|#]]
[[Category:Claimed moons of Earth]]
[[Category:Potential impact events caused by near-Earth objects]]