2021 UA1 is a small (~2 meter) near-Earth object that passed about 3047 km from the surface of Earth while passing over Antarctica on 25 October 2021 around 03:07 UT. Given the small size of the asteroid it only reached the brightness of Pluto at around apparent magnitude 14. Since it approached from the direction of the Sun, it was not discovered until 4 hours after closest approach.

Closest non-impacting asteroids to Earth, except Earth-grazing fireballs(using JPL SBDB numbers and Earth radius of 6,378 km)
AsteroidDateDistance from surface of EarthUncertainty in approach distanceObservation arcReference
2025 UC112025-10-30 12:11237 km±11 km1 day (41 obs)
2020 VT42020-11-13 17:21368 km±11 km5 days (34 obs)
2020 QG2020-08-16 04:092939 km±11 km2 days (35 obs)
2021 UA12021-10-25 03:073049 km±10 km1 day (22 obs)
2023 BU2023-01-27 00:293589 km±<1 km10 days (231 obs)
2011 CQ12011-02-04 19:395474 km±5 km1 day (35 obs)
2019 UN132019-10-31 14:456235 km±189 km1 day (16 obs)
2008 TS262008-10-09 03:306260 km±970 km1 day (19 obs)
2004 FU1622004-03-31 15:356535 km±13000 km1 day (4 obs)

The 2021 Earth approach lifted the orbit and increased the orbital period from 356 days to 413 days. This changed it from an Aten asteroid to an Apollo asteroid.

Orbital Elements
ParameterEpochPeriod (p)Aphelion (Q)Perihelion (q)Semi-major axis (a)Eccentricity (e)Inclination (i)
Units(days)AU(°)
Pre-flyby2021-Jul-01355.61.3510.6140.9820.375010.19°
Post-flyby2022-Jan-01413.11.5250.6461.0860.40460.006°
Animation of 2021 UA1's orbit around Sun - 2021 Earth approach 2021 UA1 · Mercury · Venus · Earth · Mars · Sun

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External links