Astronomy's Top Story of 2015 Question Title * What do you think was the biggest story of the year? Ceres takes center stage: Pockmarked, ice-rich surface revealed. Water abounds on moons: Oceans of possibilities in the outer solar system. Mars under water: An ocean may have once covered the red planet's northern hemisphere. Supernova hunters see quadruple: Hubble catches faraway galaxy focusing distant supernova's light. Galaxy's glow: Spacecraft spots mysterious glow at the heart of the Milky Way. Blast site discoveries: Secrets of star's death in Supernova 1987A uncovered. Earliest galaxy cluster: Scientists find the youngest galaxy cluster yet. Hints at dark matter: Dark matter annihilation may be cause of nearby gamma-ray glow. Comet visit: The European Space Agency makes a historic visit to Comet 67P. Pluto revealed: The icy world and its moons shown in stunning detail. Done