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2020 SO

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2020 SO
The orbit of 2020 SO around Earth and Sun from Nov. 2020 to Mar. 2021
Discovery [1][2]
Discovered byPan-STARRS 1
Discovery siteHaleakalā Obs.
Discovery date17 September 2020
Designations
2020 SO
P116rK2 [3]
NEO·Apollo(May 2020)[4]
Atira(Dec 2020)[2]
Orbital characteristics [2]
Epoch17 December 2020 (JD2459200.5)
Uncertainty parameter2
Observation arc167 days
Earliestprecoverydate19 August 2020
Aphelion0.988AU
Perihelion0.985 AU
0.986 AU
Eccentricity0.00181
0.98 yr (357.9 d)
276.388°
1° 0m21.877s/ day
Inclination0.1389°
216.656°
311.989°
EarthMOID0.01628 AU (May 2020)[4]
0.00106 AU (Dec 2020)
Physical characteristics
6–12m(assumed)[5]
0.0026080±0.0000001h[6]
or9.39 s
22.4(at discovery)[1]
14.1(1 Dec 2020)[7]
27.66±0.34[4]
28.43[2]

2020 SO[a]is anear-Earth objectidentified to be theCentaurupper stage used on 20 September 1966 to launch theSurveyor 2spacecraft. The object was discovered by thePan-STARRS 1survey at theHaleakala Observatoryon 17 September 2020. It was initially suspected to be anartificialobject due to its low velocity relative to Earth and later on the noticeable effects ofsolar radiation pressureon its orbit.Spectroscopicobservations by NASA'sInfrared Telescope Facilityin December 2020 found that the object's spectrum is similar to that ofstainless steel,confirming the object's artificial nature.[8]Following the object's confirmation asspace debris,the object was removed from theMinor Planet Center's database on 19 February 2021.[9]

Overview

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As it approached Earth, the trajectory indicated the geocentricorbital eccentricitywas less than 1 by 15 October 2020,[10][b]and the object becametemporarily capturedon 8 November when it entered Earth'sHill sphere.[11]It entered via the outerLagrange pointL2and will exit via Lagrange pointL1.During itsgeocentric orbitaround Earth, 2020 SO made a close approach to Earth on 1 December 2020 at aperigeedistance of approximately 0.13lunar distances(50,000 km; 31,000 mi).[4]It also made another close approach on 2 February 2021, at a perigee distance of approximately 0.58 LD (220,000 km; 140,000 mi).[4]Since discovery the time of uncertainty for February 2021 closest approach to Earth was reduced from ±3 days to less than 1 minute.[4]It left Earth's Hill sphere at around 8 March 2021.[12][b]

Photograph of the Surveyor 2Atlas-Centaurrocket booster at launch in 1966

Paul Chodasof theJet Propulsion Laboratorysuspects 2020 SO of being theSurveyor 2Centaurrocketbooster,launched on 20 September 1966.[11][12][13]The Earth-like orbit and lowrelative velocitysuggest a possible artificial object.Spectroscopymay help determine if it is covered in whitetitanium dioxidepaint.[14]Goldstone radarwill make[when?]bistatic observations transmitting from the 70-meter DSS-14 and receiving at the 34-meter DSS-13.[15]As a result of the bistatic DSS-14/RT-32 radar observations, a rotation period of about 9.5 seconds was obtained,[16]which corresponds to the photometric observations.[6]Obtained range-Doppler radar images[16]confirm that the object has an elongated shape with a length of about 10 meters and a width of about 3 meters.

Around the time of closest approach on 1 December 2020, the object was only brightened to aboutapparent magnitude14.1,[7]and required a telescope with roughly a 150mm (6 ")objective lensto be seen visually.[17]It displays a largelight curveamplitude of 2.5 magnitudes, signifying a highly elongated shape or albedo variations on its surface. It has a rotation period of approximately 9 seconds.[18]

At the time of its discovery, 2020 SO had unremarkable motion typical of amain-belt asteroid.[citation needed]However, the four observations that Pan-STARRS obtained over the course of 1.4 hours showed non-linear motion due to the rotation of the observer around Earth's axis, which is a signature of a nearby object.[1][10]

Orbital Elements for May and December 2020
Parameter Epoch Orbit
type 		Period
(p) 		Aphelion
(Q) 		Perihelion
(q) 		Semi-major
axis
(a) 		Inclination
(i) 		Heliocentric
eccentricity
(e) 		Geocentric
eccentricity
(e)[10][c]
Units (years) AU (°)
2020-May-31[4] Apollo 1.056 1.0722 1.0020 1.0371 0.14061° 0.03389 737
2020-Dec-17[2] Atira 0.980 0.9882 0.9847 0.9865 0.13842° 0.00180 0.89934
Animation of 2020 SO's orbit
Around the Sun
Around the Earth
Sun·Earth·2020 SO·Moon

In January and February 2036, it will again approach Earth with a geocentric eccentricity less than 1 since the relative velocities will be small,[10]but will not be within Earth's Hill sphere of 0.01 AU (1.5 million km).[4][d]

See also

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  • J002E3– a near-Earth object discovered in 2002 that was identified as theS-IVBthird stage of theApollo 12Saturn Vrocket
  • WT1190F– temporarily orbiting space debris that entered Earth's atmosphere in 2015
  • 2018 AV2– an artificial object discovered in a temporary orbit around Earth in 2018, now suspected to be theSnoopymodule fromApollo 10
  • 6Q0B44E– another artificial object discovered in orbit around Earth in 2018
  • Space debris
  • Temporary satellite

Notes

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  1. ^This was the 14th object ( "O" ) discovered in the first half (period "S" ) of September 2020. SeeProvisional designation in astronomy § New-style provisional designation.
  2. ^abTheJPL Horizons On-Line Ephemeris Systemshows the geocentricorbital eccentricitydropping below 1 by 15 October 2020. But a second condition for capture is that the object is within Earth'sHill spherewhich has a radius of roughly 0.01 AU (1.5 million km). Meeting both conditions is when the object is in a temporary satellite capture around Earth.
  3. ^Orbital eccentricitymust be below 1 to be orbiting the central body.
  4. ^An object needs to be within Earth'sHill sphereto truly be in orbit. An object 1AU from Earth could have a geocentric e<1 if the relative velocities are small, but we would not say it is orbiting Earth.

References

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  1. ^abc"MPEC 2020-S78: 2020 SO".Minor Planet Electronic Circular.Minor Planet Center.19 September 2020.Retrieved20 September2020.
  2. ^abcde"2020 SO".Minor Planet Center.International Astronomical Union. Archived fromthe originalon 11 February 2021.Retrieved20 September2020.
  3. ^"2020 SO".NEO Exchange.Las Cumbres Observatory.18 September 2020.Retrieved20 September2020.
  4. ^abcdefgh"JPL Small-Body Database Browser: 2020 SO"(2020-12-01 last obs.).Jet Propulsion Laboratory.Archived fromthe originalon 26 January 2021.Retrieved20 September2020.
  5. ^"NEO Earth Close Approaches".Center for Near Earth Object Studies.Jet Propulsion Laboratory.Retrieved10 October2020.
  6. ^abPeter Birtwhistle (Great Shefford Observatory)."Light curve".
  7. ^ab"2020SO Ephemerides for 1 December 2020".NEODyS(Near Earth Objects – Dynamic Site).Archivedfrom the original on 26 September 2020.Retrieved26 September2020.
  8. ^Talbert, Tricia (2 December 2020)."New Data Confirm 2020 SO to be the Upper Centaur Rocket Booster from the 1960's".NASA.Retrieved2 December2020.
  9. ^"MPEC 2021-D62: DELETION OF 2020 SO".Minor Planet Electronic Circular.Minor Planet Center.19 February 2020.Retrieved19 February2020.
  10. ^abcdHorizonsoutput."Geocentric Orbital Elements for Asteroid (2020 SO)".Retrieved27 September2020.( "Ephemeris Type" select "Orbital Elements"·"Center" select 500 for Geocentric. Output lists Eccentricity as "EC".)
  11. ^abGreicius, Tony (12 November 2020)."Earth May Have Recaptured a 1960s-Era Rocket Booster".NASA.Retrieved12 November2020.
  12. ^abDunn, Marcia (11 October 2020)."Fake asteroid? NASA expert IDs mystery object as old rocket".phys.org.Retrieved12 October2020.
  13. ^Harris, Alan (20 September 2020)."Re: another natural satellite of Earth... again".groups.io.Retrieved20 September2020.
  14. ^B., Mark (12 October 2020)."NASA Expert Believes New" Asteroid "is a Discarded Rocket Part".The Science Times.Retrieved3 November2020.Spectroscopy on the surface of 2020 SO can also determine whether it has titanium dioxide - the paint material used on space rockets.
  15. ^"Goldstone Radar Observations Planning: 2020 SO".Asteroid Radar Research.Retrieved30 November2020.
  16. ^ab"2020 SO · IAA RAS".iaaras.ru.Retrieved10 December2020.
  17. ^"Limiting Magnitude".The Wilderness Center Astronomy Club. Archived fromthe originalon 17 November 2020.Retrieved26 September2020.
  18. ^Masi, Gianluca (2 December 2020)."Near-Earth object 2020 SO: rotation and time-lapse – 01 Dec. 2020".Virtual Telescope Project.Retrieved2 December2020.
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