(29075)_1950_DA

(29075) 1950 DA

(29075) 1950 DA is a near Earth asteroid. It is notable for having the highest known probability of impacting Earth, according to the Palermo Technical Impact Hazard Scale (although this probability remains low). For a few days in December 2004 it was temporarily surpassed by 99942 Apophis (which at the time was named only by its provisional designation ).

Discovery and name

1950 DA was first discovered on February 23, 1950 by Carl A. Wirtanen at Lick Observatory. It was observed for 17 days and then lost for half a century. An object discovered on December 31, 2000 (provisionally designated ) was later recognized as a rediscovery of 1950 DA.

The asteroid has been given the number 29075, but does not yet have a name. Wirtanen had naming rights as the original discoverer; upon his death, naming rights reverted to the IAU, which may assign a name in the future.

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).

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; one trajectory misses the Earth by tens of millions of kilometers, while the other has an impact probability of ¹⁄₃₀₀.

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.