_1998_QE2%2c_Goldstone%2c_May_30%2c_2013.jpg) First radar images of1998 QE2 taken atGoldstone on 30 May 2013 | |
| Discovery[1][2][3] | |
|---|---|
| Discovered by | LINEAR |
| Discovery site | Lincoln Lab's ETS |
| Discovery date | 19 August 1998 |
| Designations | |
| (285263)1998 QE2 | |
| 1998 QE2 | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 19.24 yr (7,029 days) |
| Aphelion | 3.8092 AU |
| Perihelion | 1.0377 AU |
| 2.4234 AU | |
| Eccentricity | 0.5718 |
| 3.77 yr (1,378 days) | |
| 49.758° | |
| 0° 15m 40.32s / day | |
| Inclination | 12.859° |
| 250.14° | |
| 345.65° | |
| Knownsatellites | 1[4][a] |
| Earth MOID | 0.0345 AU (13.4 LD) |
| TJupiter | 3.239 |
| Physical characteristics | |
| S(assumed)[5] | |
(285263) 1998 QE2, provisional designation1998 QE2, is a darkasteroid and synchronousbinary system, classified asnear-Earth object andpotentially hazardous asteroid of theAmor group, approximately 3 kilometers in diameter.[7] It was discovered on 19 August 1998, by astronomers of theLINEAR program atLincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States.[2] Its sub-kilometerminor-planet moon was discovered by radar on 30 May 2013.[4][a]
As anAmor asteroid, the orbit of1998 QE2 is entirely beyond Earth's orbit. The asteroid orbits the Sun at a distance of 1.0–3.8 AU once every 3 years and 9 months (1,378 days;semi-major axis of 2.42 AU). Its orbit has aneccentricity of 0.57 and aninclination of 13° with respect to theecliptic. TheEarthminimum orbit intersection distance with the orbit of the asteroid is 0.035 AU (5,200,000 km; 3,300,000 mi), which translates into 13.4lunar distances. As with many members of the Amor group, this asteroid has anaphelion beyond the orbit ofMars (at 1.66 AU) which also makes it aMars-crosser.[1]
Thesooty surface of1998 QE2 suggested that it might have previously been acomet that experienced a close encounter with theSun.[11] However, theTisserand parameter with respect toJupiter (TJ=3.2) does not make it obvious whether1998 QE2 was ever a comet, since cometary TJ values are typically below 3.[6]
On 31 May 2013,1998 QE2 approached within 0.039 AU (5,800,000 km; 3,600,000 mi) (15lunar distances) ofEarth at 20:59UT (4:59 pm EDT).[12] This was the closest approach the asteroid will make to Earth for at least the next two centuries.[13] It is a very strong radar target forGoldstone from May 30 to June 9 and will be one forArecibo from June 6 to June 12.[6] At its closest approach the asteroid had anapparent magnitude of 11 and therefore required a small telescope to be seen.[6]
Integrating the orbital solution shows the asteroid passed 0.08 AU (12,000,000 km; 7,400,000 mi) from Earth on 8 June 1975[12] with an apparent magnitude of about 13.9.[14] The next notable close approach will be 27 May 2221, when the asteroid will pass Earth at a distance of 0.038 AU (5,700,000 km; 3,500,000 mi).[6]
Goldstoneradar observations on 29 May 2013 discovered that1998 QE2 is orbited by aminor-planet moon approximately 600–800 meters in diameter.[4][15][a] In radar images, the satellite appears brighter than1998 QE2 because it is rotating significantly more slowly, which compresses the radar return of the satellite along the Doppler axis. This makes the satellite appear narrow and bright compared to1998 QE2.[16] The satellite orbits the primary every 32 hours with a maximum separation of 6.4 kilometers (4.0 mi).[17] Once the satellite's orbit is well determined,astronomers andastrophysicists will be able to determine the mass and density of1998 QE2.
The surface of1998 QE2 is covered with asooty substance, making it optically dark with a geometricalbedo of 0.06,[6] meaning it absorbs 94% of the light that hits it, which is indicative for a carbonaceous surface of aC-type asteroid. The asteroid is covered with craters and is dark, red, and primitive.[18]
With a diameter between 2.7 and 3.2 kilometers,1998 QE2 is one of largest knownpotentially hazardous asteroid(seePHA-list).[19] Conversely, theCollaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 1.08 kilometers based on anabsolute magnitude of 17.2.[5]
![and 2 June 2013[1]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aOrbit-Asteroid-285263-1998QE2-20130602b.jpg)
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