CAPE CANAVERAL, Fla. (AP) — A spacewalking astronaut added to the millions of pieces of junk orbiting the Earth on Friday, losing a small mirror on his sleeve as soon as he emerged from the International Space Station for battery work.

Commander Chris Cassidy said the mirror quickly floated away. The lost item posed no risk to either the spacewalk or the station, according to NASA.

While millions of pieces of space debris orbit Earth, more than 20,000 items including old rocket parts and busted satellites are big enough to be tracked in order to safeguard the space station and working satellit...