The universe is cooling down, its stars pumping out about half as much energy as they did 2 billion years ago. So says a group of astronomers that has studied more than 200,000 galaxies, measuring how much energy they produce across a wide range of wavelengths. Astronomers have known since the 1990s that the total energy output from stars has been on the slide. From the birth of the first stars some 150 million years after the big bang (which created all energy and matter in the universe), nuclear fusion in their cores has been converting matter into energy—the energy that makes stars shine. But stars don’t shine forever; eventually they run out of fuel and die. Astronomers don’t know when the universe’s energy output peaked, but, according to members of the Galaxy and Mass Assembly (GAMA) project, we’re well past that point now. The GAMA team has peered through some of the largest and most powerful telescopes on the planet to explore galaxy evolution in the nearby universe. Using the Anglo-Australian Telescope, Europe’s VLT Survey Telescope and the Visible and Infrared Survey Telescope for Astronomy, and the Australian Square Kilometre Array Pathfinder, as well as orbiting observatories such as NASA’s Galaxy Evolution Explorer and Wide-field Infrared Survey Explorer and Europe’s Herschel, they found energy output from a large portion of nearby space was dropping across all of 21 different wavelengths, from ultraviolet to far infrared (see above). Releasing their data today at the International Astronomical Union general assembly in Honolulu, the GAMA team says the universe is well advanced on a long, slow decline toward a cold, dark future.