Free Astronomy Magazine March-April 2016

SPACE CHRONICLES Solved! 40 year-old mystery on the size of shadowy galaxies U sing the world’s largest tele- scopes, researchers discover- ed ancient cold gas clouds larger than galaxies in the early Uni- by KECK OBSERVATORY verse. The discovery was announced at the 227 th meeting of the Ameri- can Astronomical Society in Orlando, Florida. The discovery, led by Asso- ciate Professor Jeff Cooke, Swin- burne University of Technology, and Associate Professor John O’Meara, St. Michael’s College, has helped solve a decades-old puzzle on the nature of gas clouds, known as damped Lyman alpha systems, or DLAs. Cooke and O’Meara realized that finding DLA gas clouds in the line of sight to background galaxies T he twin 10-meter Keck telescopes, located atop Mauna Kea, are among the largest in use today. [W. M. Keck Observatory]