When a pair of neutron stars collide, they emit a fireworks show. Could some of the low-energy light produced in these mergers be detectable years later? A team of scientists thinks so — and they’re pretty sure they’ve found an example.
A Rainbow of Signals
In addition to gravitational waves, a slew of electromagnetic radiation is produced in the merger of two neutron stars, spanning the spectrum from gamma rays to radio waves.
In 2017, the now-famous neutron star collision GW170817 gave us a first look at this expected emission: it revealed a short gamma-ray burst, infrared and optical light from ejecta in a kilonova, and relatively short-lived X-ray and radio afterglows caused by high-speed outflows.
But there’s one expected type of emission that was missing from GW170817, and it’s never before been spotted in any neutron star collision: radio flaring.
Illustration of radio emission from a neutron star merger. During the merger, some neutron star matter is flung outward. This ejecta interacts with the interstellar gas, producing a years-long radio flare. [Lee et al. 2020]
Radio Secrets Revealed
Models of neutron star mergers predict that when ejecta are flung out from the stellar collision, they’ll expand into space, eventually ...