astro.wikisort.org - Asteroid

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][lower-alpha 1] 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 TS26	2008-10-09	6259 km	±1000 km	data
2004 FU162	2004-03-31	6542 km	±15000 km	data

2021 UA₁

Orbit of 2021 UA1
Discovery[1]
Discovered by	Catalina Sky Survey
Discovery date	25 October 2021
Designations
MPC designation	2021 UA1
Minor planet category	NEO Aten (pre-flyby) Apollo (post-flyby) risk listed[2]
Orbital characteristics[3]
Epoch 2021-Jul-01 (JD 2459396.5)
Uncertainty parameter 6
Observation arc	0.9 days[2]
Aphelion	1.35 AU (Q)
Perihelion	0.6139 AU (q)
Semi-major axis	0.98 AU (a)
Eccentricity	0.3750 (e)
Orbital period (sidereal)	0.97 years
Mean anomaly	312.8° (M)
Inclination	10.19° (i)
Longitude of ascending node	211.6° (Ω)
Argument of perihelion	66.27° (ω)
Earth MOID	0.000064 AU (9,600 km)
Jupiter MOID	3.7 AU (550,000,000 km)
Physical characteristics
Dimensions	~2 m (7 ft)[2] 1–3 meters
Absolute magnitude (H)	31.8[3][4]

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°

Notes

References

External links

• 2021 UA1 Close approach date: 2021 10 25.130000 (03 07 12.0) – MPC diagram using WebGL
• 2021 UA1 – Tony Dunn (Gravity Simulator)
• 2021 UA1 – David Rankin (Catalina Sky Survey)
• 2021 UA1 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• 2021 UA1 at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical Properties · Summary
• 2021 UA1 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters

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