
Three astronauts were supposed to return to earth this week from China’s Tiangong space station, but their homecoming was delayed because a piece of space junk hit the Shenzhou 20 spacecraft they were to use. They will eventually take another spacecraft home, but the incident highlights how crowded space has become. Well, "space" is pretty big, but most human space activity occurs in low-Earth orbit (LEO), which is where satellites operate. There have been discarded objects in orbit since space flight commenced, but it is growing quickly with the proliferation of multiple, sometimes hundreds, of satellites at a time, such as the Starlink system.
Space stations, spacecraft, and satellites are now equipped to perform avoidance maneuvers, but with an estimated 45,000 pieces of plastic and metal moving at up to 27,000 kilometers per hour, incidences like the damage to Shenzhou 20 will happen more often. There is also the danger of the Kessler syndrome, in which colliding space junk sets off a chain reaction, leading to massive satellite outages and exponentially more space junk. Read about the latest incident and the growing threat of space junk at Scientific American or at the Internet Archive. -via Nag on the Lake
(Image credit: xkcd)

