1991 BA

1991 BA
Discovery [1][2][3]
Discovered by Spacewatch
Discovery site Kitt Peak Obs.
Discovery date 18 January 1991
Designations
MPC designation 1991 BA
Apollo · NEO
Orbital characteristics [1]
Epoch 18 January 1991 (JD 2448274.5)
Uncertainty parameter 9
Observation arc < 1 day
Aphelion 3.6601 AU
Perihelion 0.7153 AU
2.1877 AU
Eccentricity 0.6730
3.24 yr (1,182 days)
346.82°
0° 18m 16.56s / day
Inclination 1.9376°
118.88°
70.687°
Earth MOID 0.0003 AU · 0.1 LD
Physical characteristics
Dimensions 5–10 m[4]
28.6[1]

    1991 BA is a sub-kilometer asteroid, classified as near-Earth object of the Apollo group that was first observed by Spacewatch on 18 January 1991, and passed within 160,000 km (100,000 mi) of Earth.[1][2][3] This is a little less than half the distance to the Moon.

    Description

    1991 BA is approximately 5 to 10 meters (15 to 30 ft) in diameter and is listed on the Sentry Risk Table.[4] It follows a highly eccentric (0.68), low-inclination (2.0°) orbit of 3.3 years duration, ranging between 0.71 and 3.7 AU from the Sun. 1991 BA was, at the time of its discovery, the smallest and closest confirmed asteroid outside of Earth's atmosphere.[5] 1991 BA is too faint to be observed except during close approaches to Earth and is considered lost.

    Possible impact

    Virtual clones of the asteroid that fit the uncertainty region in the known trajectory show a 1 in 1,961,000 chance that the asteroid will impact Earth on 2023 January 18.[4] It is estimated that an impact would produce an upper atmosphere air burst equivalent to 19 kt TNT,[4] roughly equal to Nagasaki's Fat Man. The asteroid would appear as a bright fireball and fragment in the air burst into smaller pieces that would hit the ground at terminal velocity producing a meteorite strewn field. Impacts of objects this size are estimated to occur approximately once a year. Asteroid 2008 TC3 was an object of similar size that was discovered less than a day before its impact on Earth on October 7, 2008 and produced a fireball and meteorite strewn field in the Sudan.

    References

    1. 1 2 3 4 "JPL Small-Body Database Browser: (1991 BA)" (1991-01-18 last obs.). Jet Propulsion Laboratory. Retrieved 2 August 2017.
    2. 1 2 "JPL Close-Approach Data: (1991 BA)" (last observation: 1991-01-18; arc: 1 day; uncertainty: 9). Retrieved 2012-03-20.
    3. 1 2 "1991 BA". Minor Planet Center. Retrieved 2 August 2017.
    4. 1 2 3 4 "Earth Impact Risk Summary: 1991 BA". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2011-08-17. Retrieved 2012-03-10.
    5. ↑ Scotti, J. V.; Rabinowitz, D. L.; Marsden, B. G. (1991). "Near miss of the Earth by a small asteroid". Nature. 354: 287–289. Bibcode:1991Natur.354..287S. doi:10.1038/354287a0.

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