LAUSR

Russia9s beleaguered space science program is hoping for a rare triumph this month. Spektr-RG, an x-ray satellite to be launched on 21 June from Kazakhstan, aims to map all of the estimated 100,000 galaxy clusters that can be seen across the universe. Containing as many as 1000 galaxies and the mass of 1 million billion suns, the clusters are the largest structures bound by gravity in the universe. Surveying them should shed light on the evolution of the universe and the nature of the dark energy that is accelerating its expansion. First proposed more than 30 years ago as part of a Soviet plan for a series of ambitious "great observatories" along the lines of NASA9s Hubble Space Telescope, Spektr-RG fell victim to cost cutting in cash-strapped, post-Soviet Russia. But the roughly €500 million satellite, which will carry German and Russian x-ray telescopes, was reborn early last decade with a new mission: not just to scan the sky for interesting x-ray sources, such as supermassive black holes gorging on infalling material, but to map enough galaxy clusters to find out what makes the universe tick.