Some of the most puzzling worlds in our telescopes’ catalogs may not be worlds at all, but relics from the first instants after the Big Bang. Instead of rocky or gaseous spheres, a handful of “planets ...

On Sept. 14, 2015, physicists attained the long-sought goal of detecting gravitational waves, the shockwaves spewed out by such cataclysmic events as the violent merger of two black holes. Now, in the ...