A signal from space first detected Aug. 14, 2019, may have come from a mystery object. And it might force physicists to rip up an old idea about black holes and neutron stars.
The signal was a gravitational wave, a ripple in space-time labeled GW190814, and seemed to indicate the collision of two wildly mismatched objects. The larger one was definitely a black hole, about 23 times the mass of our sun. And the smaller one was either a black hole or a neutron star, about 2.6 times the mass of our sun. There’s just one problem: There’s never been evidence that black holes or neutron stars of that size even existed.
Astronomers have never detected black holes lighter than five times the mass of the sun. And neutron stars seem to max out well below 2.5 solar masses. In between the two is a “mass gap” where, for uncertain reasons, no compact objects seemed to form. Until now.