Of the many galactic mysteries that the late, great physicist Stephen Hawking illuminated for us Earthlings, his insights into black holes are among the most captivating. In his final public interview, published for the first time on Monday, he discussed how recent groundbreaking work on gravitational waves shed light on how black holes form.
In his interview with the BBC, which took place in October 2017, Hawking described the implications of new research showing gravitational waves emanating from the collision of two neutron stars 130 million light-years away. “The fact that a black hole can form from the merger of two neutron stars was known from theory,” he said. “But this event is the first test, or observation. The merger probably produces a rotating, hyper-massive neutron star which then collapses to form a black hole.”
Black holes form when an immense amount of mass has been compressed into a tiny space, like at the end of a star’s life or the collision of two stars. Since the gravity in a black hole is so great that even light can’t escape, they are invisible to us. But gravitational waves — ripples in space-time caused by an event as huge as a neutron star merger — allow us to detect and study them in detail.
“This is very different from other ways of forming black holes, such as in a supernova or when a neutron star accretes matter from a normal star,” Hawking said of the neutron star merger in the BBC interview. “With careful analysis of the data and theoretical modelling on supercomputers, there is vast scope for new insights to be obtained about the dynamics of black hole formation and gamma-ray bursts.”
There is plenty we still don’t know about black holes, but Hawking served as an inspiration for many scientists determined to continue his work. Physicists are already trying to find evidence of “Hawking radiation,” a theoretical type of energy thought to radiate from black holes as a result of quantum effects. Doing so will show whether or not black holes truly destroy all information within them.
Whatever we discover about the nature of black holes, we can be grateful that Hawking left us with an escape route, in case we ever get sucked in: In 2015, he discussed the possibility that not all information that enters a black hole is trapped forever — suggesting, encouragingly, that nothing may truly fall in in the first place.