|Discovery site||Kitt Peak Obs.|
|Discovery date||18 January 1991|
|MPC designation||1991 BA|
|Apollo · NEO|
|Orbital characteristics |
|Epoch 18 January 1991 (JD 2448274.5)|
|Uncertainty parameter 9|
|Observation arc||4.6 hours|
|3.24 yr (1,182 days)|
|0° 18m 16.56s / day|
|Earth MOID||0.0003 AU · 0.1 LD|
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. This is a little less than half the distance to the Moon. With a 5 hour observation arc the asteroid has a poorly constrained orbit and is considered lost. It could be a member of the Beta Taurids.
1991 BA is approximately 5 to 10 meters (15 to 30 ft) in diameter and is listed on the Sentry Risk Table. 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. 1991 BA is too faint to be observed except during close approaches to Earth and is considered lost.
Virtual clones of the asteroid that fit the uncertainty region in the known trajectory show a 1 in 310,000 chance that the asteroid will impact Earth on 2023 January 18. It is estimated that an impact would produce an upper atmosphere air burst equivalent to 16 kt TNT, 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.
- "JPL Small-Body Database Browser: (1991 BA)" (1991-01-18 last obs.). Jet Propulsion Laboratory. Retrieved 2 August 2017.
- "JPL Close-Approach Data: (1991 BA)" (last observation: 1991-01-18; arc: 1 day; uncertainty: 9). Retrieved 20 March 2012.
- "1991 BA". Minor Planet Center. Retrieved 2 August 2017.
- "Earth Impact Risk Summary: 1991 BA". NASA/JPL Near-Earth Object Program Office. Archived from the original on 17 August 2011. Retrieved 10 March 2012.
- 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.
- Asteroid Fast Facts
- IAUC 5172: 1991 BA; 4U 0115+63; 1990c – (Central Bureau for Astronomical Telegrams 1991 January 21)
- 1991 BA at the JPL Small-Body Database