What is ‘sky trash’ and is it linked to the mystery objects shot down by US?

Nearly 2,000 balloons are launched into the sky daily, to monitor everything from the weather to specific phenomena in space

Mystery still surrounds the latest flying objects shot down by the US over northern Alaska, Canada's central Yukon territory and Lake Huron in Michigan in the last week.

Unlike the suspected Chinese surveillance balloon that was shot down off the coast of South Carolina on 4 February, US authorities have been mostly unwilling to speculate on where the last three objects originate from - or even to characterise what they are.