"L2" - Ground Zero in the Search for Dark Energy a Million Kilometers from Earth

"L2" - Ground Zero in the Search for Dark Energy a Million Kilometers from Earth: "The spiral galaxy NGC 4258, 25 million light-years away, shown in the image left, is one of many that contain visible Type Ia supernovae, which astronomers use to tell how fast the universe is expanding. Ten years ago in May astronomers announced that the universe's expansion is speeding up thanks to dark energy, a mysterious 'antigravity' that makes up 74 percent of the universe."