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.^[a]

2022 UR₄

Discovery[1][2]
Discovered by	ATLAS-MLO
Discovery site	Mauna Loa Obs.
Discovery date	20 November 2022
Designations
MPC designation	2022 WM7
Alternative designations	A10OBKV[3]
Minor planet category	NEO · Apollo[1]
Orbital characteristics[4]
Epoch 25 February 2023 (JD 2460000.5)
Uncertainty parameter 6
Observation arc	13.56 hours[1]
Aphelion	2.701 AU
Perihelion	0.831 AU
Semi-major axis	1.766 AU
Eccentricity	0.5294
Orbital period (sidereal)	2.35 yr (857.0 days)
Mean anomaly	36.030°
Mean motion	0° 25m 12.279s / day
Inclination	11.292°
Longitude of ascending node	207.182°
Time of perihelion	December 2022[4]
Argument of perihelion	238.577°
Earth MOID	0.000407 AU (60,900 km; 0.158 LD)
Jupiter MOID	2.641 AU
Physical characteristics
Mean diameter	4.4–9.9 m (assumed albedo 0.05–0.25)[5]
Absolute magnitude (H)	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).