Английская Википедия:(29075) 1950 DA

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Шаблон:Short description Шаблон:Use dmy dates Шаблон:Infobox planet Шаблон:Mp, provisional designation Шаблон:Mp, is a risk-listed asteroid, classified as a near-Earth object and potentially hazardous asteroid of the Apollo group, approximately Шаблон:Convert 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 2022, It is listed on the Sentry Risk Table with the second highest cumulative Palermo rating of −2.05 (impact risk of 1-in-34,000). Шаблон:Mp is not assigned a Torino scale rating, because the 2880 date is over 100 years in the future.

Discovery and nomenclature

Шаблон:Mp was first discovered on 23 February 1950 by Carl A. Wirtanen at Lick Observatory. It was observed for seventeen days and then lost because this 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 Шаблон:Mp on 4 January 2001. Just two hours later it was recognized as Шаблон:Mp.

Observations

On 5 March 2001, Шаблон:Mp made a close approach to Earth at a distance of Шаблон:Convert. 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 Шаблон:Mp is a retrograde rotator. Optical lightcurve analysis by Lenka Šarounová and Petr Pravec shows that its rotation period is Шаблон:Val hours. Due to its short rotation period and high radar albedo, Шаблон:Mp is thought to be fairly dense (more than 3.5 g/cm³, assuming that it has no internal strength) and likely composed of nickel–iron. In August 2014, scientists from the University of Tennessee determined that Шаблон:Mp 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.

Шаблон:Mp 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 Шаблон:Convert 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.

Position uncertainty and increasing divergence

Date	JPL SBDB nominal geocentric distance (AU)	uncertainty region (3-sigma)
2032 March 2	Шаблон:Convert	±52 km
2074 March 19	Шаблон:Convert	±131 km
2105 March 10	Шаблон:Convert	±22 km
2136 March 1	Шаблон:Convert	±1010 km
2187 March 8	Шаблон:Convert	±2795 km

Possible Earth impact

That Шаблон:Mp 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 Шаблон:Convert from Шаблон:Mp on 5 August 2150. At that distance and size, Diana will perturb Шаблон:Mp enough so that the change in trajectory is notable by 2880 (730 years later). In addition, over the intervening time, Шаблон:MpШаблон:'s rotation will cause its orbit to slightly change as a result of the Yarkovsky effect. If Шаблон:Mp 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 Шаблон:Mp 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 Шаблон:Mp 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

• Шаблон:Section link
• Asteroid impact prediction
• Earth-grazing fireball
• List of asteroid close approaches to Earth

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 Шаблон:Webarchive)
• Asteroids and comets rotation curves, CdRШаблон:Snd Observatoire de Genève, Raoul Behrend
• Discovery Circumstances: Numbered Minor Planets (25001)-(30000)Шаблон:Snd Minor Planet Center
• Шаблон:NeoDys
• Шаблон:JPL small body