Tuesday, August 11, 2009
Well, this is an unexpected press release. It seems that NASA's Spitzer Space Telescope has been able to find evidence for a collision between two planets about a thousand years ago around a star called HD 172555, about 100 light years from us. This collision is especially interesting in light of the fact that a collision between the Earth and another planet is now the dominant theory on why a planet such as ours was able to end up with a moon as large as the one we have.
Spaceref has also provided an animation showing what happens when two planets collide. Generally what happens is that the smaller planet is vaporized, the larger planet is turned into a molten mass for a while, while masses of material are thrown off into space, some of which settles into an orbit around the planet and eventually coalesces into something new as time goes on.
Impacts like these are much more frequent in younger solar systems, and this one is also quite young - a mere 12 million years old, compared to ours which has been around for 4.5 billion years.