(Cygnus X-1 artist image courtesy of Martin Kornmesser, ESA/ECF)

According to an article in Physics World today, Stephen Hawking was officially proven wrong in his belief that a well known galactic mass, Cygnus X-1, was not a black hole. The research team who confirmed that this black hole does in fact exist is from the Harvard-Smithsonian Center for Astrophysics right here in Cambridge, Mass. Not only did this research team confirm the black hole’s existence, they also discovered it is 14.8 times more massive than the Sun, spins way faster than anticipated (97% of its maximum possible speed), and that it is orbiting a blue star that is 19 times larger than its own black hole mass.

Black holes, if you recall, are created when stars run out of fuel and die. In dying, they collapse into a much smaller mass with such enormous gravity that it sucks in just about anything that comes light years near it.

First discovered in 1964 during a rocket flight, Cygnus X-1 is estimated to be 5 million years old. Found in the Cygnus the Swan constellation (also known as the Northern Cross) 6,050 light years from the sun, it is one of the strongest X-ray sources seen from Earth. X-ray emissions typically come from masses in space like the moon, stars, supernovas and black holes, so in 1971 researchers believed the constellation could include a black hole. Since its discovery Cygnus X-1 has been one of the most wildly studied astronomical objects by physicists and astronomers.

Harvard-Smithsonian researchers were able to confirm the existence of the black hole after successfully and accurately measuring its distance from Earth. From this the research team could conclude that its mass was so great that it could only be a black hole. They also discovered this black hole spins much faster than any others.

“There’s no doubt about its distance now, and there’s not much uncertainty anymore about its mass. It’s definitely a black hole,” explained Mark Reid of the Harvard-Smithsonian Center for Astrophysics to Physics Today. “Cygnus X-1 produced beautiful data and we were able to get a very accurate distance.”

In 1974 the existence of a black hole within Cygnus X-1 was a famous point of debate between physicists Stephen Hawking and Kip Thorne, with Hawking betting that the constellation did not have a black hole. Instead, he believed the dark object was a neutron star — a less extreme form of a dead star.

From his book A Brief History of Time, Hawking explained:

This was a form of insurance policy for me. I have done a lot of work on black holes, and it would all be wasted if it turned out that black holes do not exist. But in that case, I would have the consolation of winning my bet, which would win me four years of the magazine Private Eye. If black holes do exist, Kip will get one year of Penthouse. When we made the bet in 1975, we were 80% certain that Cygnus was a black hole. By now [1988], I would say that we are about 95% certain, but the bet has yet to be settled.“

However, Hawking actually backed down from the bet in 1990 after more observational data around the mass was known. The 10th anniversary edition of the book was updated to include this concession.

To learn more about the research, read the original Physics World article here.