2019 AQ3

2019 AQ3 is an inclined near-Earth object of the small Atira group from the innermost region of the Solar System, estimated to measure 1.4 kilometers (0.9 miles) in diameter. Among the hundreds of thousands known asteroids, 2019 AQ3's orbit was thought to have likely the smallest semi-major axis (0.589 AU) and aphelion (0.77 AU), that is, the orbit's average distance and farthest point from the Sun, respectively.[6] The object was first observed on 4 January 2019, by astronomers at Palomar's Zwicky Transient Facility in California, with recovered images dating back to 2015.[1][2]

2019 AQ3
Orbital diagram of 2019 AQ3, as viewed from the ecliptic pole
Discovery [1][2]
Discovered byZwicky Transient Facility
Discovery sitePalomar Obs.
Discovery date4 January 2019
(first observed only)
Designations
2019 AQ3
NEO · Atira [1][3]
Orbital characteristics [3]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 3 · 4[1]
Observation arc3.23 yr (1,181 d)
Aphelion0.7737 AU
Perihelion0.4036 AU
0.5887 AU
Eccentricity0.3143
165 days
118.50°
2° 10m 56.28s / day
Inclination47.219°
64.487°
163.15°
Earth MOID0.2259 AU (87.9 LD)
Mercury MOID0.0550 AU
Venus MOID≤ 0.0384 AU[4]
Physical characteristics
Mean diameter
1+ km (est.)[1]
1.4 km (est. at 0.08)[4][5]
17.6[1][3]

    The record for smallest semi-major axis was beaten by another asteroid, 2019 LF6, with 0.555 AU.[7]

    Orbit and classification
    Orbit of 2019 AQ3
    viewed from roughly the ascending and descending nodes of the orbit
    viewed from the ecliptic pole
    viewed face-on to the orbit

    2019 AQ3 orbits the Sun at a distance of 0.40–0.77 AU once every 5 months (165 days; semi-major axis of 0.589 AU). Its orbit has an eccentricity of 0.31 and an inclination of 47° with respect to the ecliptic.[3] The body's observation arc begins with a precovery taken by Pan-STARRS at Haleakala Observatory in October 2015, more than 3 years prior to its official first observation at the Zwicky Transient Facility on 4 January 2019.[1] It has a minimum orbit intersection distance with Earth of 0.22 AU or 88 lunar distances.[3]

    Aphelion

    2019 AQ3's orbit has the third-smallest aphelion of any known asteroid in the Solar System, never distancing itself more than 0.774 AU from the Sun (77% of Earth's average orbital distance).[6] Before its discovery, the record was held by (418265) 2008 EA32 at an aphelion of 0.804 AU, which is notably larger. 2019 AQ3's orbit also has a semi-major axis below that of Venus (0.723 AU) and an orbital period of 165 days, which is the third shortest among all asteroids.[8]

    Atira class

    2019 AQ3 is a member of the small class of Atira asteroids,[3] which are also known as Apoheles or interior-Earth objects, as their orbits are confined inside that of Earth's. This makes their discovery difficult, as they stay relatively close to the Sun when observed from Earth, never reaching a Solar elongation of more than 90°, often much less. Only 19 such asteroids are known, 14 of which still reach 90% Earth's distance from the Sun over the course of their orbit.[9]

    Inclination

    The asteroid's orbit is also highly inclined with respect to the plane of the Solar System, at more than 47°, the highest inclination of any known Atira asteroid,[9] although there are many near-Earth asteroids with even higher inclinations.[10]

    Total of 896 large near-Earth asteroid discoveries (larger than 1 km) by year and survey since 1995 (as of January 2019)[11]
      LINEAR
      NEAT
      Spacewatch
      LONEOS    		   CSS
      Pan-STARRS
      NEOWISE
      All others

    Perturbations

    On the short-term, 2019 AQ3 has a fairly quickly-changing orbit. Between 1600 AD and 2500 AD its aphelion distance lowers slightly from 0.7746 to 0.7725 AU, its perihelion distance increases slightly from 0.4025 to 0.4046 AU, and its inclination increases slightly from 47.19 to 47.25°. It is not subjected to a Kozai resonance because although its eccentricity and inclination oscillate in synchrony (when the eccentricity reaches its maximum value, the inclination is at its lowest and vice versa) over a long period of time, the value of the argument of perihelion circulates; the Earth-Moon system and Jupiter are its dominant perturbers.[12]

    Numbering and naming

    As of 2019, this minor planet has neither been numbered nor named by the Minor Planet Center.[1]

    Physical characteristics

    The object's diameter is estimated at 1.4 kilometers (0.87 miles),[4] which corresponds to an assumed geometric albedo of 0.08 for an absolute magnitude of 17.6.[5] The Minor Planet Center also considers 2019 AQ3 to be larger than 1 kilometer.[1] However, these are estimates with apparently no published measurement confirming the body's diameter. Based on a generic magnitude-to-diameter conversion, the asteroid could measure anywhere between 500 meters and 2 kilometers for an extreme albedo of 0.45 (brighter than the E-types of the Hungaria population) and 0.04 (very dark carbonaceous D- and P-types of some members in the Hildian and Jupiter trojan population), respectively.[5] As of 2019, less than 900 large (kilometer-sized) near-Earth asteroids have been discovered.[11]

    References
    1. "2019 AQ3". Minor Planet Center. Retrieved 8 January 2019.
    2. "MPEC 2019-A88 : 2019 AQ3". Minor Planet Electronic Circular. 6 January 2019. Retrieved 8 January 2019.
    3. "JPL Small-Body Database Browser: (2019 AQ3)" (2019-01-06 last obs.). Jet Propulsion Laboratory. Retrieved 8 January 2019.
    4. "2019AQ3 – Summary". ESA Space Situational Awareness – NEO Coordination Centre. Retrieved 8 January 2019.
    5. "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 8 January 2019.
    6. "JPL Small-Body Database Search Engine: Q < 0.99 AU". Jet Propulsion Laboratory. Retrieved 8 January 2019.
    7. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (25 July 2019). "Hot and Eccentric: The Discovery of 2019 LF6 as a New Step in the Quest for the Vatira Population". Research Notes of the American Astronomical Society. 3 (7): 106. Bibcode:2019RNAAS...3g.106D. doi:10.3847/2515-5172/ab346c.
    8. "JPL Small-Body Database Search Engine: asteroids and NEOs and period < 200 (d)". Jet Propulsion Laboratory. Retrieved 8 January 2019.
    9. "JPL Small-Body Database Search Engine: orbital class (IEO)". Jet Propulsion Laboratory. Retrieved 8 January 2019.
    10. "JPL Small-Body Database Search Engine: asteroids and NEOs and i > 47 (deg)". Jet Propulsion Laboratory. Retrieved 8 January 2019.
    11. "Discovery Statistics by Survey 1+ KM". CNEOS NASA/JPL. Retrieved 8 January 2019.
    12. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (1 August 2019). "Understanding the evolution of Atira-class asteroid 2019 AQ3, a major step towards the future discovery of the Vatira population". Monthly Notices of the Royal Astronomical Society. 487 (2): 2742–2752. arXiv:1905.08695. Bibcode:2019MNRAS.487.2742D. doi:10.1093/mnras/stz1437.
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