2020 XR

2020 XR is an Apollo near-Earth object and potentially hazardous asteroid roughly 390 meters (1,000 feet) in diameter. With a 5-day observation arc it was briefly listed as having a 1 in 11,000 chance of impacting Earth on 1 December 2028 placing it at the top of the Sentry Risk Table with a Palermo scale rating of -0.70.[4][5]

2020 XR
Discovery[1][2]
Discovered byPan-STARRS 2
Discovery siteHaleakala Obs.
Discovery date4 December 2020
Designations
2020 XR
Orbital characteristics[3]
Epoch 2020-May-31 (JD 2459000.5)
Uncertainty parameter 0
Observation arc7.8 years[4]
Aphelion4.0272 AU (602,460,000 km) (Q)
Perihelion0.97013 AU (145,129,000 km) (q)
2.4987 AU (373,800,000 km) (a)
Eccentricity0.61174 (e)
3.95 yr
312.19° (M)
Inclination13.947° (i)
249.74° (Ω)
8 December 2020
163.01° (ω)
Earth MOID0.00085 AU (127,000 km; 0.33 LD)
Jupiter MOID1.4 AU (210,000,000 km)
Physical characteristics
Mean diameter
~390 meters (1,000 feet)[4]
19.8[2][3]

    Discovery

    2020 XR was discovered by Pan-STARRS 2 on 4 December 2020,[2] when it was 0.426 AU (63.7 million km) from Earth and had a solar elongation of 75°. It came to perihelion on 8 December 2020. On 2 January 2021, it passed 0.328 AU (49.1 million km) from Earth.[3]

    On 13 December 2020, precovery observations from 2013, 2016, and mid-2020 extended the observation arc from 8 days to 7.8 years allowing the asteroid to be removed from the Sentry Risk Table.[2][4]

    2024

    It was the Earth perturbations of the asteroid in 2024 that determined if an impact was possible in December 2028. On 4 December 2024, the asteroid will pass 0.0147 AU (2.20 million km; 5.7 LD) from Earth with an uncertainty region of about ±800 km.[3] This will increase the asteroid's orbital period by 10 days.

    Orbital period 3 months before and after 2024-Dec-04 Earth approach
    Parameter Epoch
    (date)    		 Orbital
    Period
    Units (days)
    Pre-flyby 2024-Sep-04 1441
    Post-flyby 2025-Mar-04 1451

    2028

    On 7 November 2028, the asteroid will pass 0.121 AU (18.1 million km) from Earth.[3] By 1 December 2028 the asteroid will be 0.19 AU (28 million km) from Earth[6] with an uncertainty region of about ±10,000 km.[lower-alpha 1]

    Notes
    1. While the observation arc was only a few days, the uncertainty region on 1 December 2028 was approximately a billion km.

    References
    1. "MPEC 2020-X365 : 2020 XR". IAU Minor Planet Center. 7 December 2020. Retrieved 13 December 2020. (K20X00R)
    2. "2020 XR". Minor Planet Center. Retrieved 13 December 2020.
    3. "JPL Small-Body Database Browser: (2020 XR)" (last observation: 2020-12-12; arc: 7.8 years). Jet Propulsion Laboratory. Archived from the original on 13 December 2020. Retrieved 13 November 2020.
    4. "Earth Impact Risk Summary: 2020 XR". NASA/JPL Near-Earth Object Program Office. Archived from the original on 10 December 2020. Retrieved 13 December 2020.
    5. hohmanntransfer: 2020 XR (10 Dec 2020) (1/11000 = 9E-05)
    6. "2020XR Ephemerides for 1 December 2028". NEODyS (Near Earth Objects – Dynamic Site). Archived from the original on 12 December 2020. Retrieved 13 December 2020.
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