2021 UA1

2021 UA1
Orbit of 2021 UA1
Discovery[1]
Discovered byCatalina Sky Survey
Discovery date25 October 2021
Designations
2021 UA1
Orbital characteristics[3]
Epoch 2021-Jul-01 (JD 2459396.5)
Uncertainty parameter 6
Observation arc0.9 days[2]
Aphelion1.35 AU (Q)
Perihelion0.6139 AU (q)
0.98 AU (a)
Eccentricity0.3750 (e)
0.97 years
312.8° (M)
Inclination10.19° (i)
211.6° (Ω)
66.27° (ω)
Earth MOID0.000064 AU (9,600 km)
Jupiter MOID3.7 AU (550,000,000 km)
Physical characteristics
Dimensions
  • ~2 m (7 ft)[2]
  • 1–3 meters
31.8[3][4]

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.[5][a] Given the small size of the asteroid it only reached the brightness of Pluto at around apparent magnitude 14.[5] Since it approached from the direction of the Sun, it was not discovered until 4 hours after closest approach.[1]

Closest non-impacting asteroids to Earth, except Earth-grazing fireballs
(using JPL SBDB numbers and Earth radius of 6,378 km)
Asteroid Date Distance from
surface of Earth 		Uncertainty in
approach distance 		Observation arc Reference
2020 VT4 2020-11-13 17:21 368 km ±11 km 5 days (34 obs) data
2020 QG 2020-08-16 04:09 2939 km ±11 km 2 days (35 obs) data
2021 UA1 2021-10-25 03:07 3049 km ±10 km 1 day (22 obs) data
2023 BU 2023-01-27 00:29 3589 km ±<1 km 10 days (231 obs) data
2011 CQ1 2011-02-04 19:39 5474 km ±5 km 1 day (35 obs) data
2019 UN13 2019-10-31 14:45 6235 km ±189 km 1 day (16 obs) data
2008 TS26 2008-10-09 03:30 6260 km ±970 km 1 day (19 obs) data
2004 FU162 2004-03-31 15:35 6535 km ±13000 km 1 day (4 obs) data

The 2021 Earth approach lifted the orbit and increased the orbital period from 356 days to 413 days.[6] This changed it from an Aten asteroid to an Apollo asteroid.

Orbital Elements
Parameter Epoch Period
(p) 		Aphelion
(Q) 		Perihelion
(q) 		Semi-major axis
(a) 		Eccentricity
(e) 		Inclination
(i)
Units (days) AU (°)
Pre-flyby 2021-Jul-01[3] 355.6 1.351 0.614 0.982 0.3750 10.19°
Post-flyby 2022-Jan-01[6] 413.1 1.525 0.646 1.086 0.4046 0.006°
Animation of 2021 UA1's orbit around Sun - 2021 Earth approach
  2021 UA1 ·   Mercury  ·   Venus  ·   Earth ·   Mars  ·   Sun

Notes

  1. ^ Geocentric approach distance 0.000063 AU – 6378 km (Earth radius) is 3047 km. It passed within 4 degrees of the South celestial pole near closest approach.

References

  1. ^ a b "MPEC 2021-U95 : 2021 UA1". IAU Minor Planet Center. 26 October 2021. Retrieved 26 October 2021. (K21U01A)
  2. ^ a b c "Earth Impact Risk Summary: 2021 UA1". NASA/JPL Near-Earth Object Program Office. Retrieved 26 October 2021.
  3. ^ a b c "JPL Small-Body Database Browser: (2021 UA1)" (Under Close Approach Data select km for distance units). Jet Propulsion Laboratory. Retrieved 26 October 2021.
  4. ^ "2021 UA1 Orbit". Minor Planet Center. Retrieved 26 October 2021.
  5. ^ a b "Horizons Batch for 2021-10-25 03:06 UT". JPL Horizons. Archived from the original on 26 October 2021. Retrieved 26 October 2021.
  6. ^ a b "Horizons Batch showing epoch 2021-Jul-01 and 2022-Jan-01". JPL Horizons. Retrieved 26 October 2021.