2021 UA1

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2021 UA1
2021 UA1-orbit.png
Orbit of 2021 UA1
Discovery[1]
Discovered byCatalina Sky Survey
Discovery date25 October 2021
Designations
MPC designation
2021 UA1
Minor planet category
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
Absolute magnitude (H)
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
Asteroid Date Distance from
surface of Earth 		Uncertainty in
approach distance 		Reference
2020 VT4 2020-11-13 374 km ±25 km data
2020 QG 2020-08-16 2946 km ±20 km data
2021 UA1 2021-10-25 3047 km ±20 km data
2011 CQ1 2011-02-04 5481 km ±5 km data
2019 UN13 2019-10-31 6242 km ±200 km data
2008-10-09 6259 km ±1000 km data
2004 FU162 2004-03-31 6542 km ±15000 km 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.

External links[]

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