Astronomers with the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) have used data from the project to make the largest, most accurate 3D map yet of the light emitted by excited hydrogen in the early universe, 9 billion to 11 billion years ago. This specific form of light, called Lyman alpha, is emitted in large quantities when hydrogen atoms are exposed to a star's energy. That makes it a great tool for finding bright galaxies in this far-off time, which experienced a rash of star creation. However, the locations of fainter galaxies and gas, which also emit Lyman alpha, have remained largely unknown.
