Astronomers see this cloud just 1.8 billion years after the Big Bang. It has a tiny percentage of heavy elements, those forged in subsequent generations of stars.
Astronomers say they can use "galactoseismology" - the study of ripples in a galaxy's disk - to map the interior structure of galaxies and learn about dark matter.
Dawn spacecraft now in its lowest planned orbit above dwarf planet Ceres. These late December images are from just 240 miles (385 km) above Ceres' surface.