Fifty years later, Stephen Hawking proposed a theory about black holes, stating that their event horizons – the limits at which nothing can escape – should never contract, and his theoretical law was proven.
A team of scientists led by the Massachusetts Institute of Technology (MIT) confirmed the late physicist’s field theory with more than 95 percent accuracy using gravitational-wave observations.
The team made a breakthrough using data from GW150914, the first gravitational waves detected, created by two inductive black holes that created a new hole – an event that released large amounts of ripple energy through spacetime.
They re-analyzed the signal from gravitational waves before and after the cosmic collision and determined that the region of the event horizon had not decreased after the merger.
“It is possible that there will be a zoo of different compact objects, and some are black holes,” lead author Maximiliano Essi, a NASA Einstein Postdoctoral Fellow at MIT’s Kavli Institute for Astrophysics and Space Research, said in a statement. And Hawking’s laws, other animals may be slightly different. So, it’s not like you’ve taken this test once, and it’s over. You do it once, and that’s the beginning.
In 2019, Isi and his colleagues developed an echo-extraction technique just after the peak of GW150914 – the moment the black hole with the parent black hole collides to form a new black hole.
The team used this technique to pick out specific frequencies or tones for traces of otherwise noise, which they could then use to calculate the final mass and rotation of the black hole.
Both mass and rotation are related to the black hole’s event horizon region, leading researchers to wonder if they could compare the signal before and after the merger to confirm Hawking’s theory.
To answer the question, the team split the GW150914 signal at its peak, or fusion, and then developed a model to analyze the signal before determining the mass and rotation of the black hole in question.
The researchers calculated that each black hole has a total horizon area of about 90,734 square miles, which is about nine times the area of Massachusetts. He then used his previous technique to find a “ring” or bounce off of a newly formed black hole.
This allowed the team to calculate the area of its horizon as well as the mass of the newly formed black hole and its rotation. They found it to be 14,169 square miles – 13 times the size of the Bay State area, which includes Connecticut, Rhode Island and Vermont. “The data show with the utmost confidence that the horizon area has increased after the merger and the area law is very likely satisfied,” Issey said.
“It was a relief that our result agreed with the model we expected and confirmed our understanding of complex black hole mergers.” The team plans to further test Hawking’s field theory and other older theories of black hole mechanics, using data from its counterparts in Italy, LIGO and Virgo.
“It’s encouraging that we can think about gravitational wave data in new and innovative ways and come up with questions that we thought we couldn’t before,” Issy said. We can continue to extract pieces of information that speak directly to the pillars of what we think we understand. One day, this data may reveal something we didn’t expect.