Since the first detection of gravitational waves in 2015 — nearly a century after Albert Einstein first theorized about their existence — scientists have identified close to 100 disturbances of the fabric of space-time. Such detections can help us better understand the first seconds after the Big Bang. However, until recently, they have been difficult to predict.

Rather than waiting for black holes and supernovae to collide, sending ripples across the vastness of space, astronomers can now purposefully search for a specific subset of neutron stars that are most likely to emit gravitational-wave-causing radiation, thanks to a new paper by SDSU astrophysicists.

The result of supernova explosions, neutron stars are the densest objects in the universe. They fit 1.5 times the mass of our sun into a sphere less than a half-marathon’s distance across and can complete a full rotation up to 1000 times per second, which approaches 80 to 90 percent of the speed of light.

But if they spin too fast, these compact clusters of subatomic particles risk destabilizing completely. To help maintain an equilibrium state and avoid disintegration, neutron stars reduce their energy by emitting gravitational radiation.

Through elaborate computer calculations, SDSU researchers and their collaborators from Argentina pinpointed the Goldilocks speed of rapidly rotating neutron stars, just before the point of no return, that will be good candidates for studying gravitational waves.

“It’s now more exciting than ever before to be studying neutron stars because of new instruments that are more precise and have an unprecedented rate of observation,” said Fridolin Weber, a physics professor at San Diego State University and the principal investigator for the project.

“We know of about 3200 neutron stars but these new instruments could help us identify 40,000 to 50,000 more,” Weber continued.

In the future, the researchers hope to add the variable temperature of neutron stars into their models, which already require more than 20,000 lines of code. This will help answer more questions about the composition of neutron stars and the first compact objects in the universe, which still largely remain a mystery.

The paper was the cover story for the October 2022 issue of Galaxies. SDSU alumni Eric Bratton, Zikun Lun and Nathaniel Saavedra were also co-authors.