(285263) 1998 QE2

(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]

(285263) 1998 QE2
First radar images of 1998 QE2 taken at Goldstone on 30 May 2013
Discovery [1][2][3]
Discovered byLINEAR
Discovery siteLincoln 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 arc19.24 yr (7,029 days)
Aphelion3.8092 AU
Perihelion1.0377 AU
2.4234 AU
Eccentricity0.5718
3.77 yr (1,378 days)
49.758°
0° 15m 40.32s / day
Inclination12.859°
250.14°
345.65°
Known satellites1 [4][lower-alpha 1]
Earth MOID0.0345 AU (13.4 LD)
TJupiter3.239
Physical characteristics
Mean diameter
S (assumed)[5]

    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]

    • Orbit of 1998 QE2 on 31 May 2013
    • and 2 June 2013[1]

    Notes
    1. 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

    References
    1. "JPL Small-Body Database Browser: 285263 (1998 QE2)" (2017-11-16 last obs.). Jet Propulsion Laboratory. Retrieved 20 January 2018.
    2. "285263 (1998 QE2)". Minor Planet Center. Retrieved 20 January 2018.
    3. "MPEC 1998-Q19 : 1998 QE2". IAU Minor Planet Center. 22 August 1998. Retrieved 30 May 2013. (J98Q02E)
    4. Johnston, Wm. Robert (16 November 2014). "Asteroids with Satellites Database – (285263) 1998 QE2". Johnston's Archive. Retrieved 15 November 2017.
    5. "LCDB Data for (285263)". Asteroid Lightcurve Database (LCDB). Retrieved 20 January 2018.
    6. Dr. Lance A. M. Benner (28 May 2013). "(285263) 1998 QE2 Goldstone Radar Observations Planning". NASA/JPL Asteroid Radar Research. Retrieved 30 May 2013.
    7. Springmann, Alessondra; Taylor, Patrick A.; Nolan, Michael C.; Howell, Ellen S.; Brozovic, Marina; Benner, Lance A.; et al. (November 2014). "Radar-Derived Shape Model of Near-Earth Binary Asteroid System (285263) 1998 QE2" (PDF). American Astronomical Society. Bibcode:2014DPS....4640902S. Retrieved 20 January 2018.
    8. Oey, Julian (October 2014). "Lightcurve Analysis of Asteroids from Blue Mountains Observatory in 2013". The Minor Planet Bulletin. 41 (4): 276–281. Bibcode:2014MPBu...41..276O. ISSN 1052-8091. Retrieved 20 January 2018.
    9. Hills, Kevin (January 2014). "Asteroid Lightcurve Analysis at Riverland Dingo Observatory (RDO): 2013 Results". The Minor Planet Bulletin. 41 (1): 2–3. Bibcode:2014MPBu...41....2H. ISSN 1052-8091. Retrieved 20 January 2018.
    10. Hicks, M.; Buratt, B.; Dalba, P. (June 2013). "BVRI photometry of the Potentially Hazardous Asteroid 285263 (1998 QE2)". The Astronomer's Telegram (5121). Bibcode:2013ATel.5121....1H. Retrieved 20 January 2018.
    11. Deborah Netburn (24 May 2013). "Dark, massive asteroid to fly by Earth on May 31". Retrieved 24 May 2013.
    12. "JPL Close-Approach Data: 285263 (1998 QE2)" (last observation: 2013-05-28; arc: 14.7 years; Uncertainty=0). Retrieved 30 May 2013.
    13. "Asteroid 1998 QE2 to Sail Past Earth Nine Times Larger Than Cruise Ship". NASA/JPL Asteroid Radar Research. 15 May 2013. Retrieved 1 June 2013.
    14. "(285263) 1998QE2 Ephemerides for 8 June 1975". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 30 May 2013.
    15. "NASA Radar Reveals Asteroid Has Its Own Moon". NASA/JPL. 30 May 2013. Retrieved 30 May 2013.
    16. Emily Lakdawalla (30 May 2013). "Say "hi!" to asteroid -- actually, asteroids -- (285263) 1998 QE2". The Planetary Society. Retrieved 30 May 2013.
    17. "Radar Movies Highlight Asteroid 1998 QE2 and Its Moon". NASA. 6 June 2013. Retrieved 8 June 2013.
    18. "Arecibo Radar Sees Asteroid 1998 QE2 and Moon". Astrowatch. 15 June 2013. Retrieved 15 June 2013.
    19. "List of the Potentially Hazardous Asteroids (PHAs)". Minor Planet Center. Retrieved 20 January 2018.
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