... A Higher Dimensional Universe . ... Colorful Water Clouds Over Mars . ... The Hydra Cluster of Galaxies . ... Clusters of galaxies are the largest gravitationally bound objects in the universe. ... Forty years ago, on April 12, 1961, Soviet cosmonaut Yuri Alexseyevich Gagarin became the first human in space. ... At only 30 million light years distant and fully 60 thousand light years across, M51, also known as NGC 5194, is one of the brightest and most picturesque galaxies on the sky. ...