China’s FAST telescope maps neutral hydrogen, the cosmic gas for making stars

China’s FAST telescope has compiled the world’s largest catalogue of neutral hydrogen beyond the Milky Way, replacing a long-dominant US survey as the main reference for mapping the gas that fuels the formation of stars and galaxies.The FAST All-Sky H I Survey (FASHI), conducted with the 500-metre (1,640-foot) radio dish in southwest China’s Guizhou province, released its second batch of data this week. It contains 156,411 extragalactic sources – nearly five times the number detected by the now-defunct Arecibo Telescope in Puerto Rico.The publicly available data gives astronomers worldwide an unprecedented pool of galaxies to investigate some of the universe’s biggest questions – from how the vast cosmic web took shape, to why some galaxies thrive while others fade away.