An enormous amoeba-like structure 200 million light-years wide and made up of galaxies and large bubbles of gas is the largest known object in the universe.

Some of the gas bubbles are up to 400,000 light years across. Scientists think they formed when massive stars born early in the history of the universe exploded as supernovas and blew out their surrounding gases. Another theory is that the bubbles are giant gas cocoons that will one day give birth to new galaxies.