New research reveals size of first black hole ever discovered

19 Feb 2021

Image: © unlimit3d/

New research says that the first black hole ever detected is 50pc more massive than we previously thought.

The first black hole ever detected, located in the Cygnus X-1 system, was discovered in 1964 by a sub-orbital rocket launched from New Mexico. The rocket carried two Geiger counters, devices used for measuring ionising radiation, and the discovery sparked a new era of exploration for scientists back on Earth.

Now, new research published in Science has shed more light on Cygnus X-1, which is home to one of the closest black holes to Earth. Using a massive radio telescope spread across the US, the Very Long Baseline Array, a global team of astronomers was able to learn more about the black hole’s size.

“If we can view the same object from different locations, we can calculate its distance away from us by measuring how far the object appears to move relative to the background,” explained the project’s lead researcher, Prof James Miller-Jones of Curtin University.

“If you hold your finger out in front of your eyes and view it with one eye at a time, you’ll notice your finger appears to jump from one spot to another. It’s exactly the same principle.”

The team spent six days observing a full orbit of the black hole, comparing it to previous observations from the same system with the same telescope in 2011.

“This method and our new measurements show the system is further away than previously thought, with a black hole that’s significantly more massive,” Miller-Jones said.

The sheer size of the system is challenging how researchers understood the formation of black holes, added co-author Prof Ilya Mandel from Monash University.

“Stars lose mass to their surrounding environment through stellar winds that blow away from their surface,” Mandel said. “But to make a black hole this heavy, we need to dial down the amount of mass that bright stars lose during their lifetimes.

“The black hole in the Cygnus X-1 system began life as a star approximately 60 times the mass of the sun, and collapsed tens of thousands of years ago. Incredibly, it’s orbiting its companion star – a supergiant – every five and a half days at just one-fifth of the distance between the Earth and the sun.

“These new observations tell us the black hole is more than 20 times the mass of our sun – a 50pc increase on previous estimates.”

The team also said that Cygnus X-1 is spinning incredibly quickly, at a rate very close to the speed of light and faster than any other black hole found to date.

“Studying black holes is like shining a light on the universe’s best kept secrets; it’s a challenging but exciting area of research,” Miller-Jones said.

“As the next generation of telescopes comes online, their improved sensitivity reveals the universe in increasingly more detail, leveraging decades of effort invested by scientists and research teams around the world to better understand the cosmos and the exotic and extreme objects that exist. It’s a great time to be an astronomer.”

Watch a video animation of the Cygnus X-1 black hole here.

Lisa Ardill was careers editor at Silicon Republic until June 2021