2022 UR4

2022 UR4 is a small near-Earth asteroid that made an extremely close approach within 0.044 lunar distances (17,000 km; 11,000 mi) from Earth's center on 20 October 2022 at 22:45 UTC.[4] It was discovered about 14 hours before closest approach by the Asteroid Terrestrial-impact Last Alert System (ATLAS) survey telescope at Mauna Loa Observatory, Hawaii on 20 November 2022.[2] During the close approach, the asteroid passed above the northern hemisphere of Earth and reached a peak brightness of magnitude 10,[2] just 40 times fainter than the threshold of naked eye visibility.[lower-alpha 1]

2022 UR4
Discovery[1][2]
Discovered byATLAS-MLO
Discovery siteMauna Loa Obs.
Discovery date26 November 2022
Designations
2022 WM7
A10OBKV[3]
NEO · Apollo[1]
Orbital characteristics[4]
Epoch 25 February 2023 (JD 2460000.5)
Uncertainty parameter 6
Observation arc13.56 hours[1]
Aphelion2.701 AU
Perihelion0.831 AU
1.766 AU
Eccentricity0.5294
2.35 yr (857.0 days)
36.030°
0° 25m 12.279s / day
Inclination11.292°
207.182°
December 2022[4]
238.577°
Earth MOID0.000407 AU (60,900 km; 0.158 LD)
Jupiter MOID2.641 AU
Physical characteristics
Mean diameter
4.4–9.9 m (assumed albedo 0.05–0.25)[5]
28.90±0.45[4]

    Notes
    1. The faintest magnitude that can be seen with the naked eye is about 6.[6] Using the formula Δm = −2.5 log10(F1/F2),[6] where Δm = m1 – m2 = 6 – 10 = –4 is the magnitude difference between the naked eye limit and 2022 UR4's peak brightness, the brightness ratio F1/F2 of the naked eye limit to the peak brightness of 2022 UR4 is approximately 39.81 ≈ F1/F2 = 10(Δm/–2.5).

    References
    1. "2022 UR4". Minor Planet Center. Retrieved 30 November 2022.
    2. "MPEC 2022-U145 : 2022 UR4". Minor Planet Electronic Circular. Minor Planet Center. 21 October 2022. Retrieved 30 November 2022.
    3. "2022 UR4". NEO Exchange. Las Cumbres Observatory. 20 October 2022. Retrieved 30 November 2022.
    4. "JPL Small-Body Database Browser: (2022 UR4)" (2022-10-20 last obs.). Jet Propulsion Laboratory. Retrieved 30 November 2022.
    5. "Asteroid Size Estimator". Center for Near Earth Object Studies. NASA. Retrieved 30 November 2022.
    6. Mihos, Chris (2005). "The Magnitude Scale". Case Western Reserve University. Retrieved 30 November 2022.
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