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(29075) 1950 DA

Radar image of 1950 DA taken at Arecibo in March 2001, from a distance of 22 LD or 0.052 AU
Discovery
Discovered by	Carl A. Wirtanen
Discovery site	Lick Obs.
Discovery date	23 February 1950
Designations
MPC designation	(29075) 1950 DA
Alternative designations	1950 DA · 2000 YK66
Minor planet category	NEO · Apollo · PHA · risk listed
Orbital characteristics
Epoch 31 January 2012 (JD 2455957.5)
Uncertainty parameter 0
Observation arc	67.96 yr (24,823 d)
Aphelion	2.5619 AU
Perihelion	0.8350 AU
Semi-major axis	1.6985 AU
Eccentricity	0.5083
Orbital period (sidereal)	2.21 yr (809 d)
Mean anomaly	315.94°
Mean motion	0° 26 43.08 / day
Inclination	12.175°
Longitude of ascending node	356.74°
Argument of perihelion	224.61°
Earth MOID	0.0406 AU (15.8169 LD)
Proper orbital elements
Precession of perihelion	13.655 arcsec / yr
Precession of the ascending node	−35.824 arcsec / yr
Physical characteristics
Dimensions	1.39 km × 1.46 km × 1.07 km
Mean diameter	1.1 km 1.25±0.12 km 2.00±0.20 km
Mass	>4×10 kg
Mean density	>3.5 g/cm
Synodic rotation period	2.12160±0.00004 h
Geometric albedo	0.070 0.25
Spectral type	S EM B–V = 0.862±0.077 V–R = 0.494±0.069 V–I = 0.816±0.067
Absolute magnitude (H)	17.00 17.1 17.55±0.3 (R) 18.0

(29075) 1950 DA, provisional designation 1950 DA, is a risk–listed asteroid, classified as a near-Earth object and potentially hazardous asteroid of the Apollo group, approximately 1.1 kilometers (0.68 miles) in diameter. It once had the highest known probability of impacting Earth. In 2002, it had the highest Palermo rating with a value of 0.17 for a possible collision in 2880. Since that time, the estimated risk has been updated several times. In December 2015, the odds of an Earth impact were revised to 1 in 8,300 (0.012%) with a Palermo rating of −1.42. As of 2018, It is listed on the Sentry Risk Table with the highest cumulative Palermo rating. 1950 DA is not assigned a Torino scale rating, because the 2880 date is over 100 years in the future. However, if the impact were less than 100 years in the future, the asteroid would have been given a Torino rating of 1.

Discovery and nomenclature

1950 DA was first discovered on 23 February 1950 by Carl A. Wirtanen at Lick Observatory. It was observed for seventeen days and then lost because the short observation arc resulted in large uncertainties in Wirtanen's orbital solution. On 31 December 2000, it was recovered at Lowell Observatory and was announced as 2000 YK₆₆ on 4 January 2001. Just two hours later it was recognized as 1950 DA.

Observations

On 5 March 2001, 1950 DA made a close approach to Earth at a distance of 0.05207 AU (7.790 million km; 4.840 million mi; 20.26 LD). It was studied by radar at the Goldstone and Arecibo observatories from March 3 to 7, 2001.

The studies showed that the asteroid has a mean diameter of 1.1 km, assuming that 1950 DA is a retrograde rotator. Optical lightcurve analysis by Lenka Sarounova and Petr Pravec shows that its rotation period is 2.1216±0.0001 hours. Due to its short rotation period and high radar albedo, 1950 DA is thought to be fairly dense (more than 3.5 g/cm, assuming that it has no internal strength) and likely composed of nickel–iron. In August 2014, scientists from the University of Tennessee determined that 1950 DA is a rubble pile rotating faster than the breakup limit for its density, implying the asteroid is held together by van der Waals forces rather than gravity.

1950 DA made a distant approach to Earth on 5 February 2021. However, at that time it was half an AU away from Earth, preventing more useful astrometrics and timing that occurs when an object is closer to Earth. The next close approach that presents a good opportunity to observe the asteroid will be on 2 March 2032, when it will be 0.075 AU (11.2 million km) from Earth. The following table lists next five approaches closer than 0.10 AU. By 2136 the close approach solutions are becoming notably more divergent.

Possible Earth impact

That 1950 DA has one of the best-determined asteroid orbital solutions is due to a combination of:

• an orbit moderately inclined (12 degrees) to the ecliptic plane (reducing in-plane perturbations);
• high-precision radar astrometry, which provides its distance and is complementary to the measurements of angular positions;
• a 68-year observation arc;
• an uncertainty region controlled by resonance.

Main-belt asteroid 78 Diana (~125 km in diameter) will pass about 0.003 AU (450,000 km; 280,000 mi) from 1950 DA on 5 August 2150. At that distance and size, Diana will perturb 1950 DA enough so that the change in trajectory is notable by 2880 (730 years later). In addition, over the intervening time, 1950 DA's rotation will cause its orbit to slightly change as a result of the Yarkovsky effect. If 1950 DA continues on its present orbit, it may approach Earth on 16 March 2880, though the mean trajectory passes many millions of kilometres from Earth, so 1950 DA does not have a significant chance of impacting Earth. As of the 7 December 2015 solution, the probability of an impact in 2880 is 1 in 8,300 (0.012%).

The energy released by a collision with an object the size of 1950 DA would cause major effects on the climate and biosphere, which would be devastating to human civilization. The discovery of the potential impact heightened interest in asteroid deflection strategies.

See also

• List of exceptional asteroids § Landmark asteroids

Notes

1. A reported volume of 1.14 km × density of 3.5 g/cm yields a mass (m = d × v) of 3.99×10 kg

References

1. ^ "29075 (1950 DA)". Minor Planet Center. Retrieved 5 July 2018.
2. ^ "JPL Small-Body Database Browser: 29075 (1950 DA)" (2018-02-09 last obs.). Jet Propulsion Laboratory. Retrieved 5 July 2018.
3. "(29075) 1950DA NeoDys – Proper Elements". Retrieved 11 March 2018.
4. ^ Busch, Michael W.; Giorgini, Jon D.; Ostro, Steven J.; Benner, Lance A. M.; Jurgens, Raymond F.; Rose, Randy; et al. (October 2007). "Physical modeling of near-Earth Asteroid (29075) 1950 DA" (PDF). Icarus. 190 (2): 608–621. Bibcode:2007Icar..190..608B. doi:10.1016/j.icarus.2007.03.032. Retrieved 5 July 2018.
5. ^ Giorgini, J. D.; Ostro, S. J.; Benner, L. A. M.; Chodas, P. W.; Chesley, S. R.; Hudson, R. S.; et al. (April 2002). "Asteroid 1950 DA's Encounter with Earth in 2880: Physical Limits of Collision Probability Prediction" (PDF). Science. 296 (5565): 132–136. Bibcode:2002Sci...296..132G. doi:10.1126/science.1068191. PMID 11935024. Retrieved 5 July 2018.
6. ^ Mainzer, A. K.; Bauer, J. M.; Cutri, R. M.; Grav, T.; Kramer, E. A.; Masiero, J. R.; et al. (June 2016). "NEOWISE Diameters and Albedos V1.0". NASA Planetary Data System: EAR-A-COMPIL-5-NEOWISEDIAM-V1.0. Bibcode:2016PDSS..247.....M. Retrieved 5 July 2018.
7. Rivkin, A. S.; Binzel, R. P.; Bus, S. J. (May 2005). "Constraining near-Earth object albedos using near-infrared spectroscopy". Icarus. 175 (1): 175–180. Bibcode:2005Icar..175..175R. doi:10.1016/j.icarus.2004.11.005.
8. ^ Dandy, C. L.; Fitzsimmons, A.; Collander-Brown, S. J. (June 2003). "Optical colors of 56 near-Earth objects: trends with size and orbit". Icarus. 163 (2): 363–373. Bibcode:2003Icar..163..363D. doi:10.1016/S0019-1035(03)00087-3.
9. ^ "LCDB Data for (29075)". Asteroid Lightcurve Database (LCDB). Retrieved 5 July 2018.
10. ^ "NeoDys Near Earth Objects Dynamic Site" (Physical Info). Retrieved 11 March 2018.
11. ^ "29075 (1950 DA) Earth Impact Risk Summary". NASA/JPL Near-Earth Object Program Office. 7 December 2015. Retrieved 11 March 2018.
12. "Asteroid 1950 DA". NASA/JPL Near-Earth Object Program Office. Archived from the original on 21 July 2011. Retrieved 14 October 2011.
13. "Sentry Risk Table". NASA/JPL Near-Earth Object Program Office. Retrieved 20 March 2018. (Use Unconstrained Settings)
14. "MPEC 2001-A22 : 2000 YK66". Minor Planet Center. 4 January 2001. Retrieved 23 February 2018.
15. "MPEC 2001-A26 : 1950 DA = 2000 YK66". Minor Planet Center. 4 January 2001. Retrieved 23 February 2018.
16. ^ "JPL Close-Approach Data: 29075 (1950 DA)" (last observation: 2018-02-09; arc: 67.96 years). Retrieved 11 March 2018.
17. Farnocchia, D.; Chesley, S. R. (February 2014). "Assessment of the 2880 impact threat from Asteroid (29075) 1950 DA". Icarus. 229: 321–327. arXiv:1310.0861. Bibcode:2014Icar..229..321F. doi:10.1016/j.icarus.2013.09.022.
18. Rozitis, Ben; MacLennan, Eric; Emery, Joshua P. (13 August 2014). "Cohesive forces prevent the rotational breakup of rubble-pile asteroid (29075) 1950 DA" (PDF). Nature. 512 (7513): 174–176. doi:10.1038/nature13632. PMID 25119234.
19. "UT Research uncovers forces that hold asteroid together". University of Tennessee. 13 August 2014. Retrieved 17 August 2015.

External links

• MPEC 2001-A26 : 1950 DA = 2000 YK66 (K00Y66K). MPC 4 January 2001
• 3D model Rotating model of the asteroid (preferred rotation model is retrograde, NeoDys)
• Asteroid Lightcurve Database (LCDB), query form (info)
• Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (25001)-(30000) – Minor Planet Center
• (29075) 1950 DA at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
• (29075) 1950 DA at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters

• Minor planet object articles (numbered)
• Apollo asteroids
• Discoveries by Carl A. Wirtanen
• Potentially hazardous asteroids
• Potential impact events caused by near-Earth objects
• Astronomical objects discovered in 1950