(29075) 1950 DA

Discovery
Discovered by	Carl A. Wirtanen
Discovery date	February 23, 1950
Designations
Alternate name	2000 YK66
Minor planet category	Apollo
Orbital characteristics
Epoch March 6, 2006 (JD 2453800.5)
Aphelion	383.148 Gm (2.561 AU)
Perihelion	125.117 Gm (0.836 AU)
Semi-major axis	254.133 Gm (1.699 AU)
Eccentricity	0.508
Orbital period	808.726 d (2.21626 a)
Average orbital speed	21.30 km/s
Mean anomaly	75.965°
Inclination	12.184°
Longitude of ascending node	356.802°
Argument of perihelion	224.503°
Physical characteristics
Dimensions	1.1–1.4 km
Mass	>3,000 x 109 kg
Mean density	3.0 + g/cm³
Equatorial surface gravity	? m/s²
Escape velocity	? km/s
Rotation period	0.0884 d (2.1216 h)
Albedo	0.2-0.25
Temperature	? K
Spectral type	E or M
Absolute magnitude (H)	17.0

(29075) 1950 DA is a near Earth asteroid. It is notable for having the highest known probability of impacting Earth (although this probability remains low). For a few days in December 2004 it was temporarily surpassed by 99942 Apophis and in November 2008 the much smaller object 2008 TC3 briefly had a higher probability of impact (TC3 then impacted the Earth).

Contents 1 Discovery and name 2 Observations 3 Possible Earth impact 4 See also 5 References 6 External links

[edit] Discovery and name

1950 DA was first discovered on February 23, 1950 by Carl A. Wirtanen at Lick Observatory. It was observed for seventeen days and then lost until 2000, due to the large uncertainties in Wirtanen's orbital solution.

[edit] Observations

In 2001, 1950 DA made a close approach to the Earth coming to within 7.8 million km. 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 1.1–1.4 km. 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 g/cm³). and likely composed of nickel-iron^[1].

[edit] Possible Earth impact

If 1950 DA continues on its present orbit, it will approach near to the Earth on March 16, 2880. However, over the intervening time, its rotation will cause its orbit to change (by the Yarkovsky effect). Available radar and optical data suggest two possible pole directions^[2]; one trajectory misses the Earth by tens of millions of kilometers, while the other has an impact probability of 1 in 300.

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 has heightened interest in asteroid deflection strategies.

[edit] See also

• List of noteworthy asteroids
• Torino Scale
• Palermo scale

[edit] References

[edit] External links

• NASA Near Earth Object Program: Asteroid 1950 DA
• Catch the Wave: Asteroid-driven Tsunami in U.S. Eastern Seaboard's Future (Space.com)

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