(285263) 1998 QE2

Last updated

(285263) 1998 QE2
(285263) 1998 QE2, Goldstone, May 30, 2013.jpg
First radar images of 1998 QE2 taken at Goldstone on 30 May 2013
Discovery [1] [2] [3]
Discovered by LINEAR
Discovery site Lincoln Lab's ETS
Discovery date19 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°
Known satellites 1 [4] [lower-alpha 1]
Earth  MOID 0.0345 AU (13.4  LD)
TJupiter 3.239
Physical characteristics
Mean diameter
S (assumed) [5]

    (285263) 1998 QE2, provisional designation 1998 QE2, is a dark asteroid and synchronous binary system, classified as near-Earth object and potentially hazardous asteroid of the Amor group, approximately 3 kilometers in diameter. [7] It was discovered on 19 August 1998, by astronomers of the LINEAR program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States. [2] Its sub-kilometer minor-planet moon was discovered by radar on 30 May 2013. [4] [lower-alpha 1]

    Contents

    Classification and orbital characteristics

    As an Amor asteroid the orbit of 1998 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 an eccentricity of 0.57 and an inclination of 13° with respect to the ecliptic. The Earth minimum orbit intersection distance with the orbit of the asteroid is 0.035  AU (5,200,000  km ; 3,300,000  mi ), which translates into 13.4 lunar distances. As with many members of the Amor group, this asteroid has an aphelion beyond the orbit of Mars (at 1.66 AU) which also makes it a Mars-crosser. [1]

    The sooty surface of 1998 QE2 suggested that it might have previously been a comet that experienced a close encounter with the Sun. [11] However, the Tisserand parameter with respect to Jupiter (TJ=3.2) does not make it obvious whether 1998 QE2 was ever a comet, since cometary TJ values are typically below 3. [6]

    Earth approach

    On 31 May 2013, 1998 QE2 approached within 0.039 AU (5,800,000 km; 3,600,000 mi) (15 lunar distances) of Earth at 20:59 UT (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 for Goldstone from May 30 to June 9 and will be one for Arecibo from June 6 to June 12. [6] At its closest approach the asteroid had an apparent 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]

    Satellite

    Goldstone radar observations on 29 May 2013 discovered that 1998 QE2 is orbited by a minor-planet moon approximately 600–800 meters in diameter. [4] [15] [lower-alpha 1] In radar images, the satellite appears brighter than 1998 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 to 1998 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 and astrophysicists will be able to determine the mass and density of 1998 QE2.

    Physical characteristics

    Surface, albedo and composition

    The surface of 1998 QE2 is covered with a sooty substance, making it optically dark with a geometric albedo of 0.06, [6] meaning it absorbs 94% of the light that hits it, which is indicative for a carbonaceous surface of a C-type asteroid. The asteroid is covered with craters and is dark, red, and primitive. [18]

    Diameter

    With a diameter between 2.7 and 3.2 kilometers, 1998 QE2 is one of largest known potentially hazardous asteroid (see PHA-list). [19] Conversely, the Collaborative Asteroid Lightcurve Link assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 1.08 kilometers based on an absolute magnitude of 17.2. [5]

    Notes

    1. 1 2 3 4 5 Brozovic (2013)  Companion discovered 2013 May 29 using radar observations. Announced 2013 May 30. Primary: rotation period 4 hours (upper limit); diameter of 2.7 kilometers. Summary figures at the LCDB and NASA news NASA Radar Reveals Asteroid Has Its Own Moon, from 30 May 2013.
    2. Pravec (2013) web: photometry from June 2013. Rotation period 4.749±0.001 hours with a brightness amplitude of 0.19±0.02 mag. Quality Code of (3). Summary figures for at the LCDB and Pravec, P.; Wolf, M.; Sarounova, L. (2013) obtained by the NEO Photometric Program and collaborating projects

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    References

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