October 9, 2013 - There are over 10,000 near-Earth
objects (NEOs) that have been identified so far â€” asteroids and comets of varying sizesÂ that approach the Earthâ€™s orbital distance to within about 28 million miles (45 million km).Â Of the 10,000 discoveries, roughly 10 percent are larger than six-tenths of a mile (one kilometer) in size â€” large enough to have disastrous global consequences should one impact the Earth.
This is one of them.
First discovered in February 1950, 1950 DA is a 1.1-kilometer-wide asteroid
that was observed for 17 days and then disappeared from view. Then it was spotted again on Dec. 31, 2000 â€” literally on the eve of the 21st century. Coupled with radar observations made a few weeks later in March 2001 it was found that, along with a rather high rotation rate (2.1 hours), asteroid 1950 DA has a trajectory that will bring it very close to Earth on March 16, 2880. How close? Close enough that, within a specific 20-minute window, a collision can not be entirely ruled out.
The image above was made from radar observations by the Arecibo Observatory
in Puerto Rico in March 2001, when 1950 DA passed within 7.8 million kilometers (4.8 million miles) of Earth. Is this the mug shot of a future continent-killer?
Radar analysis and research of 1950 DA performed by NASAâ€™s Jet Propulsion Laboratory
scientists J.D. Giorgini, S. J. Ostro, Don Yeomans and several others from JPL and other institutions revealed thatÂ the impact probability from 1950 DA in March 2880 is, at most, 1 in 300 based on what is known about the asteroid so far.
1 in 300 may sound like a slim chance, but actually this represents a risk 50% greater than that of the average hazard due to all other asteroids from now to then.Â
However, thatâ€™s a maximum value. The study also noted the collision probability for 1950 DA as being in the range from 0 to 0.33%. That upper limit could increase or decrease as more is learned about the asteroid. (The next opportunity for studying 1950 DA via radar is in 2032.)
There are many factors that influence the path of an asteroid through space. Its spin rate, reflectivity (albedo), composition, mass, terrain variationsâ€¦ gravitational interactions with other bodies, some of which may not even have been discovered yetâ€¦ all of these can affect the movement of an asteroid and, more specifically, its exact position at a future point in time. While many of these things still arenâ€™t precisely known for 1950 DA, one in particular could end up being the saving grace for our descendants: the Yarkovsky effect.
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A small but important force acting upon asteroids, the Yarkovsky effect
is a â€śnudgeâ€ť created by thermal emission.