The universe is expanding—but astronomers can’t agree how fast. And NASA’s superstar observatory, the James Webb Space Telescope, just confirmed there’s a problem in our understanding of the stretching cosmos. JWST’s new measurements are the most precise of their kind, ...

An unexpected and astonishing find located more than 2.5 million light-years from Earth took top honors at the Royal Observatory Greenwich’s Astronomy Photographer of the Year awards this week. Amateur astronomers Marcel Drechsler, Xavier Strottner, and Yann Sainty captured an ...

The early universe was a stressful place for galaxies. Globs of tens to hundreds of neighboring galaxies, called galaxy clusters, would share a communal pool of hot gas—but not without drama. There was always another wayward galaxy crashing into the cluster, ...