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2020 CD3

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2020 CD3
2020 CD3imaged in colour byGemini North
Discovery [1][2]
Discovered byMt. Lemmon Survey
Discovery siteMt. Lemmon Obs.(CSS)
Discovery date15 February 2020
Designations
2020 CD3
C26FED2 [3][4]
NEO·Arjuna [5]·Apollo [6]
temporarily captured [1]·co-orbital [5]
Orbital characteristics [6]
Epoch2022-Aug-09 (JD2459800.5)
Uncertainty parameter0
Observation arc2.03 yr (742 days)
Earliestprecoverydate9 May 2018
Aphelion1.0418AU
Perihelion1.0162 AU
1.029 AU
Eccentricity0.01245
(Geocentrichyperbolice=58901)[7]
1.04 yr (381.25 d)
151.09°
0° 56m40.373s/ day
Inclination0.63407°
82.211°
49.972°
EarthMOID0.0212AU(3.17 millionkm;8.3LD)
Physical characteristics
0.9±0.1m(albedo of 0.35)[8]
1.2±0.1m(albedo of 0.23)[8]
Mass~4,900kg(est.)[9]
2.1±0.7 g/cm3[8]
1,146.8sor
19.114min(double-peaked solution)
573.4s(single-peaked solution)[8]
0.35(assumed V-type)[8]
0.23(assumed frommain belt)
V[8]
B–V=0.90±0.07[8]
V–R=0.46±0.08
R–I=0.44±0.06
>30(current)[10]
20(at discovery)[2]
31.80±0.34[6]
31.8[2]

2020 CD3(also2020CD3orCD3for short)[11][12]is a tinynear-Earth asteroid(orminimoon) that ordinarily orbits the Sun but makes close approaches to the Earth–Moon system, in which it can temporarily enterEarthorbit throughtemporary satellitecapture (TSC). It was discovered at theMount Lemmon Observatoryby astronomers Theodore Pruyne andKacper Wierzchośon 15 February 2020, as part of theMount Lemmon SurveyorCatalina Sky Survey.The asteroid's discovery was announced by theMinor Planet Centeron 25 February 2020, after subsequent observations confirmed that it was orbiting Earth.

It is the second temporary satellite of Earth discoveredin situ,after2006 RH120,which was discovered in 2006. Based on its nominal trajectory,2020 CD3was captured by Earth around 2016–2017, and escaped Earth's gravitationalsphere of influencearound 7 May 2020.[5][8][13]2020 CD3will 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.[14][15]

2020 CD3has anabsolute magnitudearound 32, indicating that it is very small in size. Assuming that2020 CD3has a lowalbedocharacteristic of dark,carbonaceousC-type asteroids,its diameter is probably around 1.9–3.5 metres (6–11 ft).[16][17]2020 CD3is classified as anArjuna asteroid,a subtype of small Earth-crossingApollo asteroidsthat have Earth-like orbits.[5]

Discovery

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Colour composite image of2020 CD3obtained by theGemini Observatoryon 24 February 2020[18]

2020 CD3was discovered on 15 February 2020, by astronomers Theodore Pruyne andKacper Wierzchośat 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.[1][18]2020 CD3was found as a faint, 20th magnitude object in theconstellationofVirgo,located about 0.0019AU(280,000 km; 180,000 mi) from Earth at the time.[19][20][a]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.[4]

The object's discovery was reported to theMinor Planet Center'sNear-Earth Object Confirmation Page(NEOCP), where a preliminary orbit was calculated from additional observations conducted at several observatories.[4]Follow-up observations of2020 CD3spanned six days since its discovery, and the object was formally announced in aMinor Planet Electronic Circularnotice issued by the Minor Planet Center on 25 February 2020. No indication ofperturbationsbysolar radiation pressurewas observed, and2020 CD3could not be linked to any known artificial object.[1]Although the evidence implied that2020 CD3is 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.[21][20]

Precoveryimages of2020 CD3have been identified back to May 2018.[2]

Nomenclature

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Upon discovery, the asteroid was given the temporary internal designation C26FED2.[4][3]After follow up observations confirming the object, it was then given theprovisional designation2020 CD3by the Minor Planet Center on 25 February 2020.[1]The provisional designation signifies the object's discovery date and year. The object has not yet been issued a permanentminor planet numberby the Minor Planet Center due to its modestobservation arcof a couple years and that it has not been observed at enoughoppositions.[22]

Orbit

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Animation of2020 CD3's orbit around Earth
2020 CD3·Moon·Earth

Prior to the temporary capture of2020 CD3,its heliocentric orbit was probably Earth-crossing, either falling into the categories of anAten-typeorbit (a < 1 AU) or anApollo-typeorbit (a > 1 AU), with the former considered to be more likely.[5]

Temporary capture

[edit]
The orbit of2020 CD3around the Earth. The white band is the orbit of the Moon.
Trajectory and orbits of2020 CD3around Earth, from 2015 to 2020.[b]

Because2020 CD3has an Earth-like heliocentric orbit, its motion relative to Earth is low, allowing for it to slowly approach the planet and be captured.[5]Nominal orbit solutions for2020 CD3suggest that it was captured by Earth between 2016 and 2017, and leftgeocentricorbit by May 2020 according to simulations of its orbit.[5][8]The geocentric orbit of2020 CD3ischaoticdue to the combined effects oftidal forcesfrom the Sun and Earth as well as repeated close encounters with the Moon.[23][21]The Moon gravitationally perturbs2020 CD3's geocentric orbit, causing it to be unstable. Over the course of2020 CD3's orbit around Earth, repeated close encounters with the Moon leads to ejection from its geocentric orbit as the Moon's perturbations can transfer enoughmomentumfor2020 CD3to escape Earth's gravitational influence.[24][23][25]

2020 CD3's orbit around Earth is highly variable and eccentric, hence predictions of its past trajectory before mid-2017 are uncertain.[17][25]Due to theYarkovsky effecton 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.[26]

Earth Approach Christmas Day 2015?[26]
Date JPL Horizons
nominalgeocentric
distance (AU) 		NEODyS
nominal geocentric
distance (AU) 		Find_Orb
nominal geocentric
distance (AU) 		ESANEOCC
nominal geocentric
distance (AU) 		MPC
nominal geocentric
distance (AU)
2015-Dec-25 0.0006AU(90 thousandkm) 0.0162 AU (2.42 million km) 0.288 AU (43.1 million km) 0.345 AU (51.6 million km) 0.834AU(124.8 millionkm)

Between September 2017 and February 2020 it made 12 close approaches to Earth,[14]during which time it was never more than 0.0112AU(1.68 millionkm) from Earth.[27]According to theJPL Small-Body Database,on 15 September 2017 it passed 12,000 km (7,500 mi) from the Moon.[6]The closest approach to Earth occurred on 4 April 2019, when it approached to a distance of 13,104 km (8,142 mi).[6][c]The final close approach in 2020 occurred on 13 February 2020 at a distance of about 41,000 km (25,000 mi) from Earth's surface.[25]The orbital period of2020 CD3around Earth ranged from 70 to 90 days.[25]2020 CD3escaped Earth'sHill sphereat roughly 0.01AU(1.5 millionkm) in March 2020[25][28]and returned to solar orbit on 7 May 2020.[5]

Escaping Geocentric Orbit 7 May 2020[d]
(assuming the Earth+Asteroid are the only objects in the Solar System)
Epoch Earth distance[28] Geocentric
eccentricity[13] 		Apogee[13] Orbital period[13]
2020-May-07 0.0189AU(2.83 millionkm) 0.9901 2.25 AU (337 million km) 693.61 years (253,341 d)
2020-May-08 0.0191 AU (2.86 million km) 1.0347

Being captured into a temporary orbit around Earth,2020 CD3is a temporarily captured object or atemporary satelliteof Earth.[1][29]2020 CD3has also been widely referred to in the media as a "mini-moon" of Earth, due to its small size.[18][16][17][30]2020 CD3is the second known temporary captured object discoveredin situaround Earth, with the first being2006 RH120discovered in 2006.[30]Other objects have also been suspected to have once been temporarily captured, including the small near-Earth asteroid1991 VGand thebolideDN160822 03.[31][32]Objects that get temporarily captured by Earth are thought to be common, though larger objects over 0.6 m (2 ft) in diameter are believed to be less likely to be captured by Earth and detected by modern telescopes.[30]

Future approaches

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2020 CD3will continue orbiting the Sun and will approach Earth on 20 March 2044, from a distance of 0.0245 AU (3.67 million km; 2.28 million mi).[14]It is unlikely that2020 CD3will be captured by Earth in the March 2044 encounter, as the approach distance is too large for capture[15]and outside of Earth'shill sphere.The next encounter will be August 2061, when it is expected to approach Earth from a nominal distance of 0.034 AU (5.1 million km; 3.2 million mi).[14]After the 2061 encounter the uncertainties in future encounters become much greater. By 2082 close approaches have a3-sigmauncertainty of±7 days.[6]

The possibility of2020 CD3impactingEarth has been considered by theJet Propulsion Laboratory'sSentry risk table.[9]JPL's solution accounts for non-gravitational forces[6]as the multi-decade motion of a very small object is greatly affected bysolar heating.Being only a few meters in size, an impact by2020 CD3would pose no threat to Earth as it would most likely fragment and disintegrate uponatmospheric entry.[20]With a cumulative impact probability of 2.5%,[9]it is listed as the most likely object to impact Earth, but because of the harmless size of2020 CD3,it is given aTorino Scalerating of 0 and a cumulativePalermo Scalerating of –5.20[9]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.[9]JPL Horizon's nominal orbit has the asteroid passing 0.00251AU(375 thousandkm) from Earth on 8 October 2082 (29 days after the virtual impactor).[33]

Physical characteristics

[edit]

2020 CD3is estimated to have anabsolute magnitude (H)around 31.7, indicating that it is very small in size.[6]Studies reported in November 2020 have determined that the asteroid is about 1–2 m (3.3–6.6 ft) in diameter.[11][12]The rotation period andalbedoof2020 CD3have not been measured due to the limited number of observations.[21]Assuming that the albedo of2020 CD3is similar to those of dark,carbonaceousC-type asteroids,the diameter of2020 CD3is around 1.9–3.5 m (6–11 ft), comparable to in size to that of a smallcar.[17][29]TheJPL Sentry risk tableestimates2020 CD3to have a mass of 4,900 kg (10,800 lb), based on the assumption that the asteroid has a diameter of 2 m (6.6 ft).[9]

See also

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Notes

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  1. ^Thecelestial coordinatesof2020 CD3at the time of discovery were13h03m33.11s+09° 10′ 43.1″.[1]SeeVirgofor constellation coordinates.
  2. ^JPL Horizons 28 Feb 2020 solution[6]
  3. ^13104km– Earth radius of6371 kmis6733 kmfrom the surface of Earth.
  4. ^Already outside of the Earth'sHill spherewhich has a radius of roughly 0.01 AU (1.5 million km).

References

[edit]
  1. ^abcdefgh"MPEC 2020-D104: 2020 CD3: Temporarily Captured Object".Minor Planet Electronic Circular.Minor Planet Center.25 February 2020.Retrieved25 February2020.
  2. ^abcd"2020 CD3".Minor Planet Center.International Astronomical Union.Retrieved25 February2020.
  3. ^ab"2020 CD3".NEO Exchange.Las Cumbres Observatory.15 February 2020.Retrieved25 February2020.
  4. ^abcd""Pseudo-MPEC" for C26FED2 ".Project Pluto. 24 February 2020. Archived fromthe originalon 25 February 2020.Retrieved25 February2020.
  5. ^abcdefghde la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (7 April 2020)."On the orbital evolution of meteoroid 2020 CD3, a temporarily captured orbiter of the Earth-Moon system".Monthly Notices of the Royal Astronomical Society.494(1): 1089–1094.arXiv:2003.09220.Bibcode:2020MNRAS.494.1089D.doi:10.1093/mnras/staa809.S2CID214605877.
  6. ^abcdefghi"JPL Small-Body Database Browser: 2020 CD3"(2020-03-22 last obs.).Jet Propulsion Laboratory.Retrieved25 February2020.
  7. ^"JPL Horizons On-Line Ephemeris for 2020 CD3 orbit of Earth (geocentric) at epoch 2022-Aug-09".JPL Horizons On-Line Ephemeris System.Jet Propulsion Laboratory.Retrieved21 August2022.Geocentric solution. Ephemeris Type: Orbital Elements / Center: @399 / Time Span: 2022-Aug-09 (to match infobox epoch)
  8. ^abcdefghiBolin, Bryce T.; Fremling, Christoffer; Holt, Timothy R.; Hankins, Matthew J.; Ahumada, Tomás; Anand, Shreya; et al. (August 2020)."Characterization of Temporarily-Captured Minimoon 2020 CD3by Keck Time-resolved Spectrophotometry ".The Astrophysical Journal.900(2): L45.arXiv:2008.05384.Bibcode:2020ApJ...900L..45B.doi:10.3847/2041-8213/abae69.S2CID221103592.
  9. ^abcdef"2020 CD3 -- Earth Impact Risk Summary".Center for Near Earth Object Studies.Jet Propulsion Laboratory.Retrieved3 March2020.
  10. ^"2020CD3".Near Earth Objects – Dynamic Site.Department of Mathematics, University of Pisa, Italy.Retrieved25 February2020.
  11. ^abCrewe, Ralph (24 November 2020)."Here's what we know about Earth's new minimoon".Universe Today.Retrieved25 November2020.
  12. ^abFedorets, Grigori; et al. (23 November 2020)."Establishing Earth's Minimoon Population through Characterization of Asteroid 2020 CD3".The Astronomical Journal.160(6): 277.arXiv:2011.10380.Bibcode:2020AJ....160..277F.doi:10.3847/1538-3881/abc3bc.S2CID227119071.
  13. ^abcd"JPL Horizons On-Line Ephemeris for 2020 CD3 orbit of Earth (geocentric) at epoch 2020-May-07".JPL Horizons On-Line Ephemeris System.Jet Propulsion Laboratory.Archivedfrom the original on 8 July 2022.Retrieved8 July2022.Geocentric solution. Ephemeris Type: Orbital Elements / Center: @399
  14. ^abcd"2020CD3 Close Approaches".Near Earth Objects – Dynamic Site.Department of Mathematics, University of Pisa, Italy.Archivedfrom the original on 23 October 2021.Retrieved1 March2020.
  15. ^abKoren, Marina (20 March 2020)."A Fleeting Moment in the Solar System".The Atlantic.Retrieved2 April2020.
  16. ^abByrd, Deborah (26 February 2020)."New image of Earth's new mini-moon".EarthSky.Retrieved26 February2020.
  17. ^abcdCrane, Leah (26 February 2020)."Earth has acquired a brand new moon that's about the size of a car".New Scientist.Retrieved27 February2020.
  18. ^abc"Gemini Telescope Images" Minimoon "Orbiting Earth — in Color!".National Optical-Infrared Astronomy Research Laboratory(Press release).National Science Foundation.27 February 2020.Retrieved28 February2020.
  19. ^"2020 CD3 Ephemerides".Near Earth Objects – Dynamic Site(Ephemerides at discovery). Department of Mathematics, University of Pisa, Italy.Retrieved28 February2020.
  20. ^abcKing, Bob (2 March 2020)."Earth Has A Mini-Moon — But Not for Long!".Sky & Telescope.Retrieved3 March2020.
  21. ^abcHowell, Elizabeth (28 February 2020)."How scientists found Earth's new minimoon and why it won't stay here forever".Space.Retrieved29 February2020.
  22. ^"How Are Minor Planets Named?".Minor Planet Center.International Astronomical Union.Retrieved29 February2020.
  23. ^abPlait, Phil(27 February 2020)."The Earth has a new minimoon! But not for long..."Bad Astronomy.Syfy Wire.Retrieved29 February2020.
  24. ^Baoyin, He-Xi; Chen, Chen; Li, Jun-Feng (June 2010). "Capturing Near Earth Objects".Research in Astronomy and Astrophysics.10(6): 587–598.arXiv:1108.4767.Bibcode:2010RAA....10..587B.doi:10.1088/1674-4527/10/6/008.S2CID119251954.
  25. ^abcdeNaidu, Shantanu; Farnocchia, Davide."Tiny Object Discovered in Distant Orbit Around the Earth".Center for Near Earth Object Studies.Jet Propulsion Laboratory.Retrieved3 March2020.
  26. ^ab"Horizons Batch for Christmas 2015 Geocentric distance"(Nominal is 0.0006 AU (90,000km)).JPL Horizons.Archivedfrom the original on 14 July 2022.Retrieved13 July2022.(JPL#27/Soln.date: 2021-Jun-25) (NEODyS-2 on 25 Dec 2015) (Find_Orb on 25 Dec 2015) (ESA NEOCC on 25 Dec 2015)
  27. ^"Horizons Batch for September 2017 – April 2020 Geocentric distance"(Maximum Apogee occurs 2020-Jan-05 @ 0.011179 (1.7 million km)).JPL Horizons.Archivedfrom the original on 11 July 2022.Retrieved11 July2022.(JPL#27/Soln.date: 2021-Jun-25) (NEODyS-2 for 5 Jan 2020)
  28. ^ab"Horizons Batch for March 2020 – May 2020 Geocentric distance"(Escaping Earth's Hill Sphere @ ~0.01au).JPL Horizons.Archivedfrom the original on 8 July 2022.Retrieved7 July2022.(JPL#27/Soln.date: 2021-Jun-25)
  29. ^abGough, Evan (27 February 2020)."Astronomers Discover a Tiny New Temporary Moon for the Earth. Welcome to the Family 2020 CD3".Universe Today.Retrieved29 February2020.
  30. ^abcBoyle, Rebecca (27 February 2020)."A New Mini-Moon Was Found Orbiting Earth. There Will Be More".The New York Times.Retrieved29 February2020.
  31. ^Tancredi, G. (September 1997). "An Asteroid in a Earth-like Orbit".Celestial Mechanics and Dynamical Astronomy.69(1/2): 119–132.Bibcode:1997CeMDA..69..119T.doi:10.1023/A:1008378316299.S2CID189823446.
  32. ^Gohd, Chelsea (2 December 2019)."Scientists Spot Rare Minimoon Fireball Over Australia".Space.Retrieved29 February2020.
  33. ^"Horizons Batch for September 2082 – November 2082 Geocentric distance"(Earth approach occurs 2082-Oct-08 06:47 @ 0.002507 AU).JPL Horizons.Retrieved10 July2022.(JPL#27/Soln.date: 2021-Jun-25)
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