There have been small objects colliding in space before, but now we have two full fledged satellites that have run into each other. An Iridium communication satellite collided with an old Russian Cosmos Communication satellite. This collision created hundreds of new pieces of debris that could in turn collide with other satellites. The collision occurred about 500 miles over Siberia.
The first thing most people are concerned about is the International Space Station or Hubble. Both of these orbit a lot lower, so they are not in immediate danger from this debris. However, there are a lot of satellites in similar orbits to these to that are now at increased risk of collision with space debris.
A company called Analytic Graphics created a pretty neat animation of the collision and the resulting debris cloud (based computer models of course).
You can see the debris spread out fairly quickly. When they add all the other objects up there it starts looking pretty crowded.
You can even listen for radar echos from the debris cloud. Spaceweather is streaming the Air Force Space Surveillance Radar signals from Texas. The next time to listen is 11:56pm to 12:07am EST tonight.
Reprinted with permission from the Half-Astrophysicist Blog.