Hao Ding

Double neutron stars are pairs of ultra-dense remnants of exploded massive stars. They orbit each other and gradually spiral closer until they merge in a powerful flash — a source of gravitational waves. But where do such pairs actually form? One possibility is inside star clusters, where stars are plentiful and interact closely.

Gravity satellites have noticed that Earth's gravity field breathes imperceptibly with a period of about six years. It's as if an invisible pendulum swings the planet from within, and every six years the scale's needle shifts slightly. The signal turned out to be so clean that it could be separated from the noise of oceans and melting glaciers.