Implicit 'which is', 'which are'
A new study has shown that millions of pieces of junk floating in space could be a big hazard for satellites orbiting Earth.
Is there an implicit 'which are' in front of floating in space? Why is 'which are' not written?
This is a reduced relative clause. We delete unnecessary elements of sentences to make them shorter and easier to read. The missing words are which are or that are.