Quasars, at billions of light-years from Earth the most distant observable objects in the universe, are believed to be the cores of galaxies in an early stage of development.
这个句子的主结构很清晰,我想问的是,插入语at billions of light-years from Earththe most distant observable objects in the universe中,红色部分是同位语还是定语从句,是用来修饰Earth还是Quasars的? 求各种知情人士一解该青年心头之躁!