2023 BU

2023 BU is a near-Earth object that passed 9,967 ± 1 km (6,193.21 ± 0.62 mi) from the centerpoint of Earth around 27 January 2023 00:29 UT.[3] Since Earth's radius is about 6,378 km (3,963 mi), it was expected to pass approximately 3,589 ± 1 km (2,230.10 ± 0.62 mi) from the surface of Earth over the southern tip of South America.[7] It passed at an altitude above low Earth orbit which is 2,000 km (1,200 mi) and below geostationary orbit which is 36,000 km (22,000 mi). The asteroid is about 3–8 meters in diameter[5] and approached Earth from the night sky. It is the fourth closest non-impacting approach known to Earth (excluding Earthgrazers) after 2020 VT4, 2020 QG, and 2021 UA1.

2023 BU
Radar image of 2023 BU by the Goldstone Solar System Radar on 29 January 2023
Discovery[1][2]
Discovered byGennadiy Borisov
Discovery siteMARGO, Nauchnyi, Crimea
Discovery date21 January 2023
Designations
2023 BU
gb00553
NEO · Apollo
Orbital characteristics[3]
Epoch 25 February 2023 (JD 2460000.5)
(Post-flyby orbit)
Uncertainty parameter 1
Observation arc10 days (231 obs)[3]
Aphelion1.230 AU
Perihelion0.9840 AU
1.107 AU
Eccentricity0.1111
1.16 yr
28.7°
Inclination3.75°
125.5°
27 January 2023 04:30[4]
355.8°
Earth MOID0.00046 AU (69,000 km; 0.18 LD)
Physical characteristics
Mean diameter
3–8 meters (CNEOS)[5]
~77 seconds[6]
29.4±0.5 (JPL)[3]
29.4 (MPC)[1]

    Orbital details
      2023 BU ·    Earth ·    Sun

    The asteroid came to perihelion (closest approach to the Sun) on 27 January 2023,[4] four hours after closest approach with Earth. 2023 BU was first imaged by Gennadiy Borisov at Nauchnyi, Crimea, on 21 January 2023 23:53 UT,[2] about five days before closest approach. It was last observed on 31 January 2023.[1]

    2023 BU closest Earth approach on 2023-Jan-27 00:29 UT[3]
    Date and time of closest approach Earth distance
    (AU)    		 Sun distance
    (AU)    		 Velocity
    wrt Earth
    (km/s)    		 Velocity
    wrt Sun
    (km/s)    		 Uncertainty region
    (3-sigma)    		 Reference
    2023-01-27 00:290.000067 AU (10,000 km; 0.0261 LD)0.985 AU (147.4 million km; 383 LD)9.335.2± <1 kmHorizons

    The gravitational effect of the 2023 Earth approach will increase the orbital period from 359 days to an estimated 425 days.[8] It will lift the perihelion and aphelion distances. The relatively low Earth encounter speed of 9.3 km/s (21,000 mph) is a result of a low eccentricity and Earth-like orbit.

    Orbital elements
    Parameter Epoch Period
    (p)    		 Aphelion
    (Q)    		 Perihelion
    (q)    		 Semi-major axis
    (a)    		 Eccentricity
    (e)    		 Inclination
    (i)
    Units (days) AU (°)
    Pre-flyby 2022-Oct-25[8] 358.91.050.9260.9880.0632.35°
    Post-flyby 2023-Feb-25[3] 425.41.230.9841.110.1113.75°

    Impact assessment

    There was no risk of an Earth impact during the 2023 Earth approach. Assuming the asteroid is at the larger size estimate of 8 meters in diameter, if it had entered the atmosphere it would not have reached the ground intact and would breakup around 30 km above the ground, thus representing only minimal threat to life.[9]

    Impacts by objects 8 meters (26 ft) in diameter occur, on average, every 5 years; impacts by objects 4 meters (13 ft) in diameter happen, on average, once every year.[9] 2023 BU has a 1 in 17 million chance of impacting Earth on 20 January 2110.[10]

    History of 2023 BU closest approach uncertainties for the 3500–3600 km pass of Earth's surface
    JPL SBDB
    solution    		 Observation arc Date and time of closest approach Uncertainty region
    (3-sigma)[lower-alpha 1]
    JPL 11 day (25 obs)2023-01-26 21:17 ± 02:22[11]± 2,600 km[12]
    JPL 22 days (30 obs)2023-01-27 00:17 ± 01:05[13]± 1,700 km[14]
    JPL 33 days (42 obs)2023-01-27 00:28 ± 00:10[15]± 262 km[16]
    JPL 43 days (39 obs)2023-01-27 00:26 ± 00:10[17]± 260 km[18]
    JPL 54 days (65 obs)2023-01-27 00:28 ± 00:02[19]± 29 km[20]
    JPL 64 days (61 obs)2023-01-27 00:28 ± 00:02[21]± 27 km[22]
    JPL 95 days (121 obs)2023-01-27 00:29 ± <00:01± 5 km[23]
    JPL 115 days (143 obs)2023-01-27 00:29 ± <00:01[24]± 2 km[25][lower-alpha 2]
    JPL 126 days (166 obs)2023-01-27 00:29 ± <00:01[5]± 0.3 km[26]
    JPL 136 days (191 obs)2023-01-27 00:29 ± <00:01± 0.2 km[27]
    JPL 146 days (194 obs)2023-01-27 00:29 ± <00:01± 0.19 km[28]
    JPL 156 days (199 obs)2023-01-27 00:29 ± <00:01± 0.18 km[29]
    JPL 1910 days (231 obs)2023-01-27 00:29 ± <00:01± 0.15 km[30]
    JPL 2110 days (238 obs)2023-01-27 00:29 ± <00:01± 0.13 km[31]
    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 VT42020-11-13 17:21368 km±11 km5 days (34 obs)data
    2020 QG2020-08-16 04:092939 km±11 km2 days (35 obs)data
    2021 UA12021-10-25 03:073049 km±10 km1 day (22 obs)data
    2023 BU2023-01-27 00:293589 km±<1 km10 days (231 obs)data
    2011 CQ12011-02-04 19:395474 km±5 km1 day (35 obs)data
    2019 UN132019-10-31 14:456235 km±189 km1 day (16 obs)data
    2008 TS262008-10-09 03:306260 km±970 km1 day (19 obs)data
    2004 FU1622004-03-31 15:356535 km±13000 km1 day (4 obs)data

    See also

    Notes
    1. The JPL SBDB time of closest approach can vary by a minute from the Horizons time of closest approach giving them slightly different uncertainty regions. Horizons values are calculated using the JPL SBDB time of closest approach.
    2. JPL#11 Soln.date: 2023-Jan-26_15:02:34 PST was the active solution at the time of closest approach "2023-Jan-26 16:29 PST".

    References
    1. "2023 BU". Minor Planet Center. Retrieved 28 January 2023.
    2. "MPEC 2023-B72 : 2023 BU". Minor Planet Electronic Circular. Minor Planet Center. 22 January 2023. Retrieved 22 January 2023.
    3. "JPL Small-Body Database Browser: (2023 BU)". Jet Propulsion Laboratory. Archived from the original on 22 January 2023. Retrieved 28 January 2023.
    4. "Perihelion @ 0.984AU on 27 Jan 2023" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 26 January 2023.
    5. Archive JPL 12 CNEOS Close Approaches
    6. Northolt Branch Observatory: 77 seconds with an amplitude of 0.9 mag
    7. "NASA System Predicts Small Asteroid to Pass Close by Earth This Week". Jet Propulsion Laboratory. 25 January 2023. Retrieved 26 January 2023.
    8. "Horizons Batch showing epoch 2022-Oct-25 and 2023-Feb-25". JPL Horizons. Retrieved 24 January 2023.
    9. Robert Marcus; H. Jay Melosh; Gareth Collins. "Earth Impact Effects Program". Imperial College London / Purdue University. Retrieved 24 January 2023. (using 8-meter diameter, density of 3000 kg/m3, speed of 11.4 km/s, and impact angle of 45°)
    10. "Earth Impact Risk Summary: 2023 BU". NASA/JPL Near-Earth Object Program Office. Retrieved 11 February 2023.
    11. Archive JPL 1 SBDB
    12. Archive JPL 1 Horizons
    13. Archive JPL 2 CNEOS Close Approaches
    14. Archive JPL 2 Horizons
    15. Archive JPL 3 CNEOS Close Approaches
    16. Archive JPL 3 Horizons
    17. Archive JPL 4 CNEOS Close Approaches
    18. Archive JPL 4 Horizons
    19. Archive JPL 5 CNEOS Close Approaches
    20. Archive JPL 5 Horizons
    21. Archive JPL 6 CNEOS Close Approaches
    22. Archive JPL 6 Horizons
    23. Archive JPL 9 Horizons
    24. Archive JPL 11 CNEOS Close Approaches
    25. Archive JPL 11 Horizons
    26. Archive JPL 12 Horizons
    27. Archive JPL 13 Horizons
    28. Archive JPL 14 Horizons
    29. Archive JPL 15 Horizons
    30. Archive JPL 19 Horizons
    31. Archive JPL 21 Horizons
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