 | This article needs to beupdated. The reason given is:New Arecibo radar results presented at the 8th IAA Planetary Defense Conference in April 2023[1]. Please help update this article to reflect recent events or newly available information.(April 2023) |
 Arecibo Observatory radar image of1998 OR2 with a crater on 18 April 2020 | |
| Discovery[2][3] | |
|---|---|
| Discovered by | NEAT |
| Discovery site | Haleakala Obs. |
| Discovery date | 24 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 arc | 35.49 yr (12,963 days) |
| Earliestprecovery date | 30 June 1987 (Siding Spring Obs.) |
| Aphelion | 3.750AU |
| Perihelion | 1.011 AU |
| 2.380 AU | |
| Eccentricity | 0.5754 |
| 3.67yr (1,342 days) | |
| 280.159° | |
| 0° 16m 6.082s / day | |
| Inclination | 5.878° |
| 26.942° | |
| 174.580° | |
| Earth MOID | 0.00866 AU (3.37 LD) |
| Physical characteristics[1]: 6 | |
| Dimensions | 2.08 × 1.93 × 1.60 km (±0.10 × 0.10 × 0.03 km) |
| 1.78±0.10 km | |
| 10.67 km2 | |
| Volume | 3.0±0.5 km3 |
Meandensity | 3.2±0.2 g/cm3 |
| 4.10872±0.00001 h | |
| 69.3°±5° (wrtecliptic)[a] | |
| 332.3°±5° | |
| 20.7°±5° | |
| 0.15[5] | |
| Xn orS[5] | |
| 15.72±0.02[6] 16.04[2][3] | |
(52768) 1998 OR2 (provisional designation1998 OR2) is anasteroid on aneccentric orbit, classified as anear-Earth object andpotentially hazardous asteroid of theAmor group, with a diameter of 2 kilometers (1.2 mi). It was discovered on 24 July 1998, by astronomers of theNear-Earth Asteroid Tracking (NEAT) program at theHaleakala 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 anobservation arc of 37.27 years (13612 days),[2] 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]
_09.04.2020.gif)
1998 OR2 is a member of the dynamicalAmor group ofnear-Earth asteroids,[2][3] and therefore does not currently crossEarth's orbit. The asteroid's closest approach to the Sun is just outside Earth's farthest distance from the Sun. When the asteroid has aperihelion point less than 1.017 AU (Earth's aphelion), it is classified anApollo asteroid. This asteroid's category flips back and forth as time passes, due to minorperturbations 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 higheccentricity of 0.57 and aninclination of 6° with respect to theecliptic. With its sufficiently largeaphelion, this asteroid is also classified as aMars-crosser, crossing the orbit of Mars at 1.66 AU.[2]
The body'sobservation arc begins with aprecovery published by theDigitized Sky Survey taken at theSiding Spring Observatory in June 1986, more than 12 years prior to its official discovery observation atHaleakala Observatory, Hawaii.[3]
With anabsolute magnitude of approximately 15.8,[3]1998 OR2 is one of the brightest and presumably largest-knownpotentially hazardous asteroids (seePHA-list).[7] It currently has an Earthminimum orbital intersection distance of 0.0087 AU (1,300,000 km), which translates into 3.4lunar 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 09:56UTC, 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-yearobservation 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.)
| 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 |
| (671294)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 5lunar distances (LD) of objects withH 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 onH andalbedo range between X and Y. (D) Reference: data source from theJPL SBDB, withAU converted into LD (1 AU≈390 LD) (E) Color codes: unobserved at close approach observed during close approach upcoming approaches | |||||||
According to observations by theNASA IRTF telescope during the ExploreNEOs Warm Spitzer program,1998 OR2 is a rather rareL-type asteroid.[10] Delay-Doppler radar observations by theArecibo Observatory in April 2020 have shown that1998 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]
In 2009, rotationallightcurves of1998 OR2 were obtained fromphotometric observations by astronomers in Salvador, Brazil, and during theLowell Observatory Near-Earth Asteroid Photometric Survey (NEAPS). Lightcurve analysis gave arotation period of 3.198 and 4.112 hours with a brightness amplitude of 0.29 and 0.16magnitude, 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]
The Collaborative Asteroid Lightcurve Link (CALL) assumes a standardalbedo for stony asteroids of 0.20 and calculates a diameter of 2.15 km (1.34 mi) based on anabsolute magnitude of 15.7.[15] It is the first near-earth asteroid to show evidence ofshock darkening: the slow darkening of the surface over time, from micrometeorites and solar wind.[5]
As of 2023, thisminor planet has not beennamed.[3]
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