The huge, 100-foot-tall (30 meters) core of a Chinese rocket is tumbling wildly through low-Earth orbit and could make an uncontrolled reentry through the atmosphere in the coming days, according to news reports.

The core belongs to a Long March 5B rocket (a version of China’s largest rocket), which successfully launched a module for China’s planned Tianhe space station into orbit on Wednesday (April 28). Following the module’s deployment, the rocket core was expected to make maneuvers for a controlled reentry into Earth’s atmosphere, according to SpaceNews — however, that didn’t happen.