Einstein’s theory of General Relativity has withstood every test for more than a century.
From the bending of starlight to orbital decay, Einstein’s predictions for spacetime’s behavior have never failed.
Since 2015, the final stages of black hole and neutron star inspirals and mergers have been observed directly.
The holy grail of black hole mergers, however, would be an inspiraling system that we could monitor consistently throughout the decay process, culminating in a merger.
Neutron stars are no better; the binaries we’ve found won’t result in a collision for some 80 million years.
Over in Andromeda, the nearest large galaxy to the Milky Way, a number of unusual systems have been found.
One of them, J0045+41, was originally thought to be two stars orbiting one another with a period of just 80 days.
When additional observations were taken in the X-ray, they revealed a surprise: J0045+41 weren’t stars at all.
Instead, Trevor Dorn-Wallenstein’s team discovered a distant supermassive black hole pair, purely by coincidence.
Powerful relativistic effects will cause this orbit to decay, leading to a merger within 1,000 years.
A long-period space-based gravitational wave detector would see the orbit, inspiral, and merger as it unfolds: a cosmic first.