|Discovery site||Lincoln Lab's ETS|
|Discovery date||11 September 1999|
|MPC designation||101955 Bennu|
|Apollo · NEO · PHA|
|Epoch 31 July 2016 (JD 2457600.5)|
|Uncertainty parameter 0|
|Observation arc||13.36 yr (4880 days)|
|Aphelion||1.3559 AU (202.84 Gm)|
|Perihelion||0.89689 AU (134.173 Gm)|
|1.1264 AU (168.51 Gm)|
|1.20 yr (436.65 d)|
Average orbital speed
|0° 49m 28.056s / day|
|Earth MOID||0.0032228 AU (482,120 km)|
|Jupiter MOID||3.87795 AU (580.133 Gm)|
|Jupiter Tisserand parameter||5.525|
|Proper orbital elements|
Proper mean motion
|301.1345 deg / yr|
Proper orbital period
|±10 m 275|
|Mass||6.0×1010 kg to 7.76×1010 kg|
|1.26 ± 0.070 g/cm3|
Equatorial surface gravity
|4.288 h (0.1787 d)|
|176 ± 2°|
101955 Bennu (provisional designation 1999 RQ36) is a carbonaceous asteroid in the Apollo group, and classified as a potentially hazardous object, with a 1 in 2700 chance of impacting Earth in the 22nd century. It was discovered by the LINEAR Project on September 11, 1999. It is the planned target of the OSIRIS-REx mission which is intended to return samples to Earth in 2023 for further study. It is a potential Earth impactor and is listed on the Sentry Risk Table with the third highest rating on the Palermo Technical Impact Hazard Scale.
101955 Bennu has a mean diameter of approximately 492 m (1,614 ft; 0.306 mi) and has been observed extensively with the Arecibo Observatory Planetary Radar and the Goldstone Deep Space Network.
Possible Earth impact
On average, an asteroid with a diameter of 500 m (1,600 ft; 0.31 mi) can be expected to impact Earth about every 130,000 years or so. A 2010 dynamical study by Andrea Milani and collaborators predicted a series of eight potential Earth impacts by Bennu between 2169 and 2199. The cumulative probability of impact is dependent on physical properties of Bennu that were poorly known at the time, but was not found to exceed 0.071% for all eight encounters. The authors recognized that an accurate assessment of 101955 Bennu's probability of Earth impact would require a detailed shape model and additional observations (either from the ground or from spacecraft visiting the object) to determine the magnitude and direction of the Yarkovsky effect.
After the publication of the shape model and astrometry based on radar observations obtained in 1999, 2005, and 2011, it was possible to estimate the Yarkovsky acceleration and to revise the impact assessment. The current (as of 2014) best estimate of the impact probability is a cumulative probability of 0.037% in the interval 2175 to 2196. This corresponds to a score on the Palermo scale of −1.70.
101955 Bennu has been considered as the target of spacecraft missions due to the low Δv required to reach it from Earth orbit. The OSIRIS-REx mission of NASA's New Frontiers Program is planned to launch in September 8, 2016, reach 101955 Bennu in 2019, and return samples to Earth in 2023.
The name Bennu was selected from more than eight thousand student entries from dozens of countries around the world who entered a "Name That Asteroid!" contest run by the University of Arizona, The Planetary Society, and the LINEAR Project. A third-grade student named Michael Puzio, from North Carolina proposed the name in reference to the Egyptian mythological bird Bennu. To Puzio, the OSIRIS-REx spacecraft with its extended TAGSAM arm resembles the Egyptian deity, which is typically depicted as a heron.
Artist concept of OSIRIS-REx at asteroid Bennu.
Animation of OSIRIS-REx collecting a sample from asteroid Bennu.
- Nolan, M. C.; Magri, C.; Howell, E. S.; Benner, L. A. M.; Giorgini, J. D.; Hergenrother, C. W.; Hudson, R. S.; Lauretta, D. S.; Margot, J. L.; Ostro, S. J.; Scheeres, D. J. (2013). "Shape model and surface properties of the OSIRIS-REx target Asteroid (101955) Bennu from radar and lightcurve observations". Icarus. 226 (1): 629–640. Bibcode:2013Icar..226..629N. doi:10.1016/j.icarus.2013.05.028. ISSN 0019-1035.
- "Goldstone Delay-Doppler Images of 1999 RQ36". Asteroid Radar Research. Jet Propulsion Laboratory.
- "JPL Small-Body Database Browser: 101955 Bennu (1999 RQ36)" (2013-01-20 last obs.). Jet Propulsion Laboratory. Retrieved 20 August 2016.
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- "Planetary Habitability Calculators". Planetary Habitability Laboratory. University of Puerto Rico at Arecibo. Retrieved 6 December 2015.
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- Lauretta, D. S.; Bartels, A. E.; et al. (April 2015). "The OSIRIS-REx target asteroid (101955) Bennu: Constraints on its physical, geological, and dynamical nature from astronomical observations". Meteoritics & Planetary Science. 50 (4): 834–849. doi:10.1111/maps.12353.
- Brown, Dwayne; Neal-Jones, Nancy (March 31, 2015). "RELEASE 15-056 – NASA's OSIRIS-REx Mission Passes Critical Milestone". NASA. Retrieved April 4, 2015.
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- Hudson, R. S.; Ostro, S. J.; Benner, L. A. M. "Recent Delay-Doppler Radar Asteroid Modeling Results: 1999 RQ36 and Craters on Toutatis". Bulletin of the American Astronomical Society. American Astronomical Society. 32: 1001. Bibcode:2000DPS....32.0710H.
- Robert Marcus; H. Jay Melosh & Gareth Collins (2010). "Earth Impact Effects Program". Imperial College London / Purdue University. Retrieved 2013-02-07. (solution using density of 2,600 kg/m^3, sped of 17km/s, and impact angle of 45 degrees)
- Milani, Andrea; Chesley, Steven R.; Sansaturio, Maria Eugenia; Bernardi, Fabrizio; Valsecchi, Giovanni B.; Arratia, Oscar (2009). "Long term impact risk for (101955) 1999 RQ36". Icarus. 203 (2): 460–471. arXiv:. Bibcode:2009Icar..203..460M. doi:10.1016/j.icarus.2009.05.029.
- Chesley, Steven R.; Farnocchia, Davide; Nolan, Michael C.; Vokrouhlický, David; Chodas, Paul W.; Milani, Andrea; Spoto, Federica; Rozitis, Benjamin; Benner, Lance A.M.; Bottke, William F.; Busch, Michael W.; Emery, Joshua P.; Howell, Ellen S.; Lauretta, Dante S.; Margot, Jean-Luc; Taylor, Patrick A. (2014). "Orbit and bulk density of the OSIRIS-REx target Asteroid (101955) Bennu". Icarus. 235: 5–22. arXiv:. Bibcode:2014Icar..235....5C. doi:10.1016/j.icarus.2014.02.020. ISSN 0019-1035.
- Near-Earth Asteroid Delta-V for Space Rendezvous
- Brown, Dwayne; Neal-Jones, Nancy (January 15, 2014). "NASA RELEASE 14-017 - NASA Invites Public to Send Names on an Asteroid Mission and Beyond". NASA. Retrieved January 16, 2014.
- Earth Impact Risk Summary: 101955 1999 RQ36 (Years: 2169–2199) – JPL near-Earth object website
- Orbit parameters – NASA website
- Temperature History and Dynamical Evolution of (101955) 1999 RQ 36: A Potential Target for Sample Return from a Primitive Asteroid (2011 ApJ 728 L42)
- Physical Properties of OSIRIS-REx Target Asteroid (101955) 1999 RQ36 derived from Herschel, ESO-VISIR and Spitzer observations (arXiv:1210.5370 : 19 Oct 2012)
- The Design Reference Asteroid for the OSIRIS-REx Mission Target (101955) Bennu (arXiv:1409.4704 : 16 Sep 2014)
- 101955 Bennu at the JPL Small-Body Database