Andrew L. Miller

A neutron star is a super-dense remnant of a supernova explosion, where a teaspoon of matter weighs a billion tons. Many of them, as discovered back in 1967 by Jocelyn Bell Burnell, become pulsars — cosmic lighthouses that regularly flash in the radio band.

Two teams of bridge builders were working on opposite banks of a chasm. One was throwing a crossing from the light-mass side, where signals stretch on for hours like a slow hum. The other was building from the far edge, where heavy pairs plunge into merger within seconds, like a landslide. Between them yawned a void: chirp masses from 0.01 to 0.1 solar masses.