Space experts have worried that a speeding bit of orbital debris might one day smash a large spacecraft into hundreds of pieces and start a chain reaction, a slow cascade of collisions that would expand for centuries, spreading chaos through the heavens.

China’s test on Jan. 11 of an antisatellite rocket that shattered an old satellite into hundreds of large fragments added about 1000 more detectable objects to the current 10,000. That means the chain reaction will most likely start sooner. If experts’ predictions are right, the cascade could put billions of dollars’ worth of advanced satellites at risk and eventually threaten to limit humanity’s reach for the stars.