Sunday, November 6, 2011

Asteroid 2005 YU55 will not hit the Moon either

Left image: Orbit of 2005 YU55 at closest approach as seen from above. Right Image: Orbit of 2005 YU55 at closest approach as seen from the side. The asteroid is significantly above the plane of Earth's orbit. Simulated in Celestia (Click to embiggen).



Animation of the trajectory of asteroid 2005 YU55 compared to the orbits of the Earth and the Moon on 8-9 November 2011. Image credit NASA/JPL

Richard Hoagland has been saying that asteroid 2005 YU55 will hit the Moon.

His reason for saying this, apart from some numerical co-incidences which are just that, coincidences (perihelions of YU55 2011-09-09.8, C2010 X1 is 2011-09-10.7, spooky), is that the "close" encounter of Comet C/2010 X1 Elenin and YU55 changed YU55's orbit.

Unfortunately for his thesis, at that time Elenin was a stream of dust and rubble not up to deflecting the orbit of anything much. Also, we know that a close encounter between Comet Elenin when it was still intact and the asteroid 1999 RQ176 failed to deflect that asteroid.

Now, 1999 RQ176 is roughly 3 km in diameter compared to 0.4 Km for 2005 YU55, but it was also 100 times closer to Elenin (0.002 AU compared to 0.2 AU for Elenin and YU55) and gravitational force falls off as the square of the distance, so the gravitational deflection of YU55 by Elenin will be for all practical purposes non-existent.

And you would need substantial deflection, look at the animation above (and see also here), to hit (or zoom just above) the Moon would require a significant change of orbit, not just the minuscule deflection an incoherent cloud of dust could cause. What I wrote of YU55 and Earth applies here; a 50% margin of difference in the orbit would still cause the asteroid to miss the Moon by 120,000 Km.

As well, it has to twist the orbit completely, the plane of the asteroids orbit lies above that of the Earth and Moon (see diagrams above and here). To cause that big an orbital change requires a large gravitational filed, not the field of a cloud of dust.

But then again, Richard Hoagladn thinks that the "encounter" between Elenin and YU55 is "intelligently designed" to communicate a message to us.

Frankly, I think alien intelligences have better ways of communicating than with a game of cosmic billiards


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