‘Replication games’ test the robustness of social-science studies - Nature

Some galaxies glow with sweeping spiral arms, while others are shaped by violent collisions, powerful black holes, and explosive bursts of star formation. A newly released collection of 16 images from NASA's Chandra X-ray Observatory and other telescopes reveals the extraordinary diversity of these cosmic structures. Like precious gemstones, galaxies come in many shapes and sizes, each with characteristics that tell a story about its history. Astronomers generally classify them into three major groups. Spiral galaxies, including our Milky Way, have winding arms extending from their centers. Elliptical galaxies typically contain older stars and are often thought to form through galactic mergers. Irregular galaxies have less orderly structures and can display a wide variety of cosmic activity.