Can a new X-ray telescope finally find the universe's missing matter?

The universe is missing about 40% of its atoms—they should be in a diffuse, hot gas strung between galaxies called the WHIM. Fisher et al. used simulations to show that NewAthena, an upcoming X-ray observatory, can detect this hidden material by watching absorption lines it imprints on bright X-ray sources. They mapped out exactly how long observations need to be and how bright the background source must shine to confirm a detection.