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(52768) 1998 OR2

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(52768) 1998 OR2 (provisional designation 1998 OR2) is an asteroid on an eccentric orbit, classified as a near-Earth object and potentially hazardous asteroid of the Amor group, with a diameter of 2 kilometers (1.2 mi). It was discovered on 24 July 1998, by astronomers of the Near-Earth Asteroid Tracking (NEAT) program at the Haleakala Observatory, Hawaii, it passed very near to earth on 29 April 2020 at around 4:15am.[3] It is one of the brightest and therefore largest potentially hazardous asteroids known to exist.[7] With an observation arc of 35 years, the asteroid has a well-determined orbit, and its trajectory is well known through the year 2197.[2] The asteroid's orbit is only potentially hazardous on a time scale of thousands of years.[8]

(52768) 1998 OR2
Arecibo Observatory radar image of 1998 OR2 with a crater on 18 April 2020
Discovery[2][3]
Discovered byNEAT
Discovery siteHaleakala Obs.
Discovery date24 July 1998
Designations
(52768) 1998 OR2
1998 OR2
Amor · NEO · PHA[2][3]
Orbital characteristics[2]
Epoch 25 February 2023 (JD 2460000.5 )
Uncertainty parameter 0
Observation arc35.49 yr (12,963 days)
Earliest precovery date30 June 1987 (Siding Spring Obs.)
Aphelion3.750 AU
Perihelion1.011 AU
2.380 AU
Eccentricity0.5754
3.67 yr (1,342 days)
280.159°
0° 16m 6.082s / day
Inclination5.878°
26.942°
174.580°
Earth MOID0.00866 AU (3.37 LD)
Physical characteristics[1]: 6 
Dimensions2.08 × 1.93 × 1.60 km
(± 0.10 × 0.10 × 0.03 km)
1.78±0.10 km
10.67 km2
Volume3.0±0.5 km3
Mean density
3.2±0.2 g/cm3
4.10872±0.00001 h
69.3°±5° (wrt ecliptic)[a]
20.7°±5°
332.3°±5°
0.15[5]
Xn or S[5]
15.72±0.02[6]
16.04[2][3]

Orbit and classification

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Time lapse of asteroid 1998 OR2's motion in the sky on 9 April 2020
 
Orbit diagram of 1998 OR2
 
Arecibo radar images of 1998 OR2 taken over a two-hour period in April 2020
 
Animation of 1998 OR2 close approach in 2020

1998 OR2 is a member of the dynamical Amor group of near-Earth asteroids,[2][3] and therefore does not currently cross Earth's orbit. The asteroid's closest approach to the Sun is just outside Earth's farthest distance from the Sun. When the asteroid has a perihelion point less than 1.017 AU (Earth's aphelion), it is classified an Apollo asteroid. This asteroid's category flips back and forth as time passes, due to minor perturbations of its orbit.

It orbits the Sun at a distance of 1.0–3.7 AU once every 3 years and 8 months (1,344 days; semi-major axis of 2.38 AU). Its orbit has a high eccentricity of 0.57 and an inclination of 6° with respect to the ecliptic. With its sufficiently large aphelion, this asteroid is also classified as a Mars-crosser, crossing the orbit of Mars at 1.66 AU.[2]

The body's observation arc begins with a precovery published by the Digitized Sky Survey taken at the Siding Spring Observatory in June 1986, more than 12 years prior to its official discovery observation at Haleakala Observatory, Hawaii.[3]

Close approaches

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With an absolute magnitude of approximately 15.8,[3] 1998 OR2 is one of the brightest and presumably largest-known potentially hazardous asteroids (see PHA-list).[7] It currently has an Earth minimum orbital intersection distance of 0.0087 AU (1,300,000 km), which translates into 3.4 lunar distances (LD).[2] On 16 April 2079, this asteroid will make a near-Earth encounter at a safe distance of 0.0118 AU (4.59 LD), and pass the Moon at 0.0092 AU (3.6 LD).[2] The asteroid's orbit is only potentially hazardous on a time scale of hundreds, if not thousands, of years.

On 29 April 2020 at 09:56 UTC, the asteroid passed at a distance of 0.042 AU (6.3 million km; 16 LD) from Earth.[2] With observations as recent as April 2020 and a 32-year observation arc, the 2020 close approach distance was known with an accuracy of roughly ±6 km.[9] (For comparison, Venus will be 0.29 AU or 43 million km or 110 LD from Earth on 3 June 2020.)

History of close approaches of large near-Earth objects since 1908 (A)
PHA Date Approach distance (lunar dist.) Abs.
mag
(H) 		Diameter (C)
(m) 		Ref (D)
Nomi-
nal(B) 		Mini-
mum 		Maxi-
mum
(33342) 1998 WT24 1908-12-16 3.542 3.537 3.547 17.9 556–1795 data
(458732) 2011 MD5 1918-09-17 0.911 0.909 0.913 17.9 556–1795 data
(7482) 1994 PC1 1933-01-17 2.927 2.927 2.928 16.8 749–1357 data
69230 Hermes 1937-10-30 1.926 1.926 1.927 17.5 668–2158 data
69230 Hermes 1942-04-26 1.651 1.651 1.651 17.5 668–2158 data
(137108) 1999 AN10 1946-08-07 2.432 2.429 2.435 17.9 556–1795 data
(33342) 1998 WT24 1956-12-16 3.523 3.523 3.523 17.9 556–1795 data
(163243) 2002 FB3 1961-04-12 4.903 4.900 4.906 16.4 1669–1695 data
(192642) 1999 RD32 1969-08-27 3.627 3.625 3.630 16.3 1161–3750 data
(143651) 2003 QO104 1981-05-18 2.761 2.760 2.761 16.0 1333–4306 data
2017 CH1 1992-06-05 4.691 3.391 6.037 17.9 556–1795 data
(170086) 2002 XR14 1995-06-24 4.259 4.259 4.260 18.0 531–1714 data
(33342) 1998 WT24 2001-12-16 4.859 4.859 4.859 17.9 556–1795 data
4179 Toutatis 2004-09-29 4.031 4.031 4.031 15.3 2440–2450 data
2014 JO25 2017-04-19 4.573 4.573 4.573 17.8 582–1879 data
(137108) 1999 AN10 2027-08-07 1.014 1.010 1.019 17.9 556–1795 data
(35396) 1997 XF11 2028-10-26 2.417 2.417 2.418 16.9 881–2845 data
(154276) 2002 SY50 2071-10-30 3.415 3.412 3.418 17.6 714–1406 data
(164121) 2003 YT1 2073-04-29 4.409 4.409 4.409 16.2 1167–2267 data
(385343) 2002 LV 2076-08-04 4.184 4.183 4.185 16.6 1011–3266 data
(52768) 1998 OR2 2079-04-16 4.611 4.611 4.612 15.8 1462–4721 data
(33342) 1998 WT24 2099-12-18 4.919 4.919 4.919 17.9 556–1795 data
(85182) 1991 AQ 2130-01-27 4.140 4.139 4.141 17.1 1100 data
314082 Dryope 2186-07-16 3.709 2.996 4.786 17.5 668–2158 data
(137126) 1999 CF9 2192-08-21 4.970 4.967 4.973 18.0 531–1714 data
(290772) 2005 VC 2198-05-05 1.951 1.791 2.134 17.6 638–2061 data
(A) List includes near-Earth approaches of less than 5 lunar distances (LD) of objects with H brighter than 18.
(B) Nominal geocentric distance from the Earth's center to the object's center (Earth radius≈0.017 LD).
(C) Diameter: estimated, theoretical mean-diameter based on H and albedo range between X and Y.
(D) Reference: data source from the JPL SBDB, with AU converted into LD (1 AU≈390 LD)
(E) Color codes:   unobserved at close approach   observed during close approach   upcoming approaches

Physical characteristics

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Animation of radar images showing 1998 OR2's rotation

According to observations by the NASA IRTF telescope during the ExploreNEOs Warm Spitzer program, 1998 OR2 is a rather rare L-type asteroid.[10] Delay-Doppler radar observations by the Arecibo Observatory in April 2020 have shown that 1998 OR2 bears a large, crater-like concavity in its shape.[11] These radar observations have also resolved several other topographic features on the asteroid's surface, such as hills and ridges.[12]

Rotation period

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In 2009, rotational lightcurves of 1998 OR2 were obtained from photometric observations by astronomers in Salvador, Brazil, and during the Lowell Observatory Near-Earth Asteroid Photometric Survey (NEAPS). Lightcurve analysis gave a rotation period of 3.198 and 4.112 hours with a brightness amplitude of 0.29 and 0.16 magnitude, respectively (U=2/2+).[13][14] The latter rotation period of 4.1 hours was later confirmed by radar observations of the asteroid in 2020.[12][11]

Diameter and albedo

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The Collaborative Asteroid Lightcurve Link (CALL) assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 2.15 km (1.34 mi) based on an absolute magnitude of 15.7.[15] It is the first near-earth asteroid to show evidence of shock darkening: the slow darkening of the surface over time, from micrometeorites and solar wind.[5]

Naming

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As of 2023, this minor planet has not been named.[3]

Notes

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  1. ^ 1998 OR2's rotational north pole direction is given in terms of ecliptic coordinates, where λ is ecliptic longitude and β is ecliptic latitude.[1]: 6  β is the angular offset from the ecliptic plane, whereas inclination i with respect to the ecliptic is the angular offset of the asteroid's rotational north pole from the ecliptic north pole at β = +90° ; i with respect to the ecliptic would be the complement of β.[4] Therefore, given β = +20.7° , i = 90° – (+20.7°) = 69.3° from the ecliptic.

References

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  1. ^ a b c Devogèle, Maxime; et al. (5 April 2023). (52768) 1998 OR2, an analog to (16) Psyche in the near-Earth space?. 8th IAA Planetary Defense Conference. Vienna, Austria. p. 9. Archived from the original on 5 April 2023.
  2. ^ a b c d e f g h i j "Small-Body Database Lookup: 52768 (1998 OR2)" (2022-12-26 last obs.). Jet Propulsion Laboratory. Retrieved 5 April 2023.
  3. ^ a b c d e f g h "52768 (1998 OR2)". Minor Planet Center. Retrieved 7 March 2020.
  4. ^ "Coordinate transformations". Astronomy and Astrophysics. European Southern Observatory. January 1998. Archived from the original on 17 June 2021. Retrieved 5 April 2023.
  5. ^ a b c Battle, Adam; Reddy, Vishnu; Sanchez, Juan A.; Sharkey, Benjamin; Pearson, Neil; Bowen, Bryn (September 2022). "Physical Characterization of Near-Earth Asteroid (52768) 1998 OR2: Evidence of Shock Darkening/Impact Melt". The Planetary Science Journal. 3 (9): 13. arXiv:2210.03049. Bibcode:2022PSJ.....3..226B. doi:10.3847/PSJ/ac7223. 226.
  6. ^ Husárik, Marek; Ivanova, Oleksandra (September 2021). Photometric results of two PHAs: (52768) 1998 OR2 and (99942) Apophis. 16th Europlanet Science Congress 2022. Vol. 16. Granada, Spain: Europlanet Society. Bibcode:2022EPSC...16..671H. doi:10.5194/epsc2022-671. EPSC2022-671.
  7. ^ a b "List of the Potentially Hazardous Asteroids (PHAs)". Minor Planet Center. Retrieved 24 January 2018.
  8. ^ 1998OR2 MOID over the next 2700 years – Peter Thomas
  9. ^ JPL #277 (solution date: 2020-Apr-29) (MaxDist of 0.0420485754979265) – (MinDist of 0.0420484977243086) * 149597870.7 = 12 km
  10. ^ Thomas, Cristina A.; Emery, Joshua P.; Trilling, David E.; Delbó, Marco; Hora, Joseph L.; Mueller, Michael (January 2014). "Physical characterization of Warm Spitzer-observed near-Earth objects". Icarus. 228: 217–246. arXiv:1310.2000. Bibcode:2014Icar..228..217T. doi:10.1016/j.icarus.2013.10.004. S2CID 119278697.
  11. ^ a b Virkki, A. K. (23 April 2020). "Arecibo Continues Operations through Pandemic to Observe Potentially Hazardous Asteroid 1998 OR2". Planetary Radar Science Group. NAIC-Arecibo Observatory. Retrieved 23 April 2020.
  12. ^ a b Kotala, Zenaida Gonzalez (23 April 2020). "Asteroid Visiting Earth's Neighborhood Brings its Own Face Mask". UCF Today. University of Central Florida. Retrieved 23 April 2020.
  13. ^ Betzler, Alberto Silva; Novaes, Alberto Brum (October 2009). "Photometric Observations of 1998 OR2, 1999 AQ10, and 2008 TC3". The Minor Planet Bulletin. 36 (4): 145–147. Bibcode:2009MPBu...36..145B. ISSN 1052-8091.
  14. ^ Koehn, Bruce W.; Bowell, Edward G.; Skiff, Brian A.; Sanborn, Jason J.; McLelland, Kyle P.; Pravec, Petr; et al. (October 2014). "Lowell Observatory Near-Earth Asteroid Photometric Survey (NEAPS) - 2009 January through 2009 June". The Minor Planet Bulletin. 41 (4): 286–300. Bibcode:2014MPBu...41..286K. ISSN 1052-8091.
  15. ^ "LCDB Data for (52768)". Asteroid Lightcurve Database (LCDB). Retrieved 7 March 2020.
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