According to “Ria Novosti” in a Jan. 26, 2011 story, Russian astronomers have predicted that an asteroid may impact Earth on Friday, April 13, 2036.
But first, the asteroid named “Apophis” will transit within 37,000 to 38,000 kilometers (about 23,000 miles) on April 13, 2029. During that time there is a very small possibility that Apophis could possibly pass through a gravitational keyhole that would generate specific effects which could result in an actual collision with Earth’s surface in 2036. At present, the National Aeronautics and Space Admin. evaluates this possibility at 1 in 250,000 (4 in a million) and that is a probability of zero on the Torino Scale.
The operative term for this report is “may.” The astronomer, Professor Leonid Sokolov of the St. Petersburg State University, made very clear that, according to the news story: “. . .the chance of a collision in 2036 was extremely slim saying that the asteroid would likely disintegrate into smaller parts and smaller collisions with Earth could occur in the following years.”
There are some astronomers and observers who consider it possible that the 2029 transit by Apophis could be as close as 18,300 miles and that this would alter the subsequent orbit enough to vastly increase the possibility of an impact trajectory with Earth in 2036. As a result, the Russians and the European Space Agency may look into the need for and the possibility of manufacturing some space device to divert this asteroid.
In 2013, Apophis will pass within 14,400,000 million km (about 8.9 million miles) and astronomers will be able to get more precise measurements to predict the 2029 and 2036 transits, according to “USA Today.”
The overall accuracy of identifying these near Earth objects and predicting their orbits contains large margins of error. On Jan. 13, 2011, “RIA Novosti” reported an object passed within 130,000 km (80,796 miles) of Earth. Named “2010 AL30 . . . ‘The asteroid posed no danger anyway,’ said astronomer Leonid Yelenin from the Moscow-based Keldysh Institute of Applied Mathematics. He classified asteroids of over 100 meters in diameter as being dangerous.” The article goes on, “Yelenin also said the calculations were not quite exact: the asteroid that was expected to come closest to Earth at about 12:48 GMT did so at 06:45 GMT.”
For Apophis, there are two functions that may affect its position and potential danger, and both processes can be applied to all near Earth objects. The first is “orbital resonance”; the second is the “Yarkovsky effect.”
Orbital resonance is the result of two bodies in space that exert gravitational forces on each other in a certain ratio. This can generate an unstable orbit where they shift positions to eliminate the resonance. The Wikipedia explanation is useful in this context. Whether this may apply to Apophis has not been determined and it has been identified as worth studying by NASA.
The Yarkovsky effect is caused by differences in temperatures on the sunny side and the dark side of objects in space. The Jet Propulsion Laboratories explanation is an easy-to-read article that demonstrates how this could change the orbit of Apophis.
Because of these various effects, Apophis will be the subject of close observation in 2013 as NASA, the European Space Agency and Russian astronomers keep track of it and other potentially dangerous near Earth objects.