The captioned topic is more popular since the new movie “Gravity” was released. Space.com has a short briefing on orbital debris – I can’t vouch for the accuracy, but if correct, this is interesting:
The majority of catalogued objects (65 percent) result from a Chinese anti-satellite test in 2007, and the accidental collision of two satellites in 2009. When objects in different orbits intersect, the collision takes place at a speed of thousands of miles per hour.
We recommend the movie “Gravity”, bearing in mind that it is entertainment, not a documentary. IEEE Spectrum looked at the space junk issue on the day of the “Gravity” release:
The Kessler syndrome imagines a situation where the thousands of pieces of space junk in Earth orbit begin to multiply as accidental collisions create even more debris over time. In 2012, Donald Kessler and Darren McKnight argued in IEEE Spectrum that the sheer density of space debris leftover from decades of spacecraft and satellite launches, explosions and collisions had already reached a mathematical tipping point that would enable a runaway debris scenario.
Space debris already poses a very real danger to both astronauts and satellites, even when it’s not rapidly multiplying like the sped-up Kessler syndrome envisioned in “Gravity.” The ever-growing cloud of space junk has occasionally forced the International Space Station to dodge out of the way and even go into emergency evacuation mode. It also poses a danger for satellites, as was graphically illustrated in a 2009 collision between an active Iridium communications satellite and a defunct Russian satellite.