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2021 UA1

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Earth-crossing asteroid

2021 UA1
Orbit of 2021 UA1
Discovery
Discovered byCatalina Sky Survey
Discovery date25 October 2021
Designations
MPC designation2021 UA1
Minor planet category
Orbital characteristics
Epoch 2021-Jul-01 (JD 2459396.5)
Uncertainty parameter 6
Observation arc0.9 days
Aphelion1.35 AU (Q)
Perihelion0.6139 AU (q)
Semi-major axis0.98 AU (a)
Eccentricity0.3750 (e)
Orbital period (sidereal)0.97 years
Mean anomaly312.8° (M)
Inclination10.19° (i)
Longitude of ascending node211.6° (Ω)
Argument of perihelion66.27° (ω)
Earth MOID0.000064 AU (9,600 km)
Jupiter MOID3.7 AU (550,000,000 km)
Physical characteristics
Dimensions
  • ~2 m (7 ft)
  • 1–3 meters
Absolute magnitude (H)31.8

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)
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. 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-01 355.6 1.351 0.614 0.982 0.3750 10.19°
Post-flyby 2022-Jan-01 413.1 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. ^ "MPEC 2021-U95 : 2021 UA1". IAU Minor Planet Center. 26 October 2021. Retrieved 26 October 2021. (K21U01A)
  2. ^ "Earth Impact Risk Summary: 2021 UA1". NASA/JPL Near-Earth Object Program Office. Retrieved 26 October 2021.
  3. ^ "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. ^ "Horizons Batch for 2021-10-25 03:06 UT". JPL Horizons. Archived from the original on 26 October 2021. Retrieved 26 October 2021.
  6. ^ "Horizons Batch showing epoch 2021-Jul-01 and 2022-Jan-01". JPL Horizons. Retrieved 26 October 2021.

External links

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