Astronomers have long struggled to clock the speed and power of Cygnus X-1, a famous stellar-mass black hole located roughly 7,200 light-years away. 

The black hole was clearly a beast, yet the data to prove its true workload remained elusive.

Now, thanks to a global network of radio telescopes and a bit of cosmic wind-watching, a Curtin University-led team has finally estimated the speed of its massive jets.

Surprisingly, the study reveals that these jets blast material into space at 150,000 kilometers per second (93,205 miles per second). That is half the speed of light.

To put into perspective, the power output of these jets is equivalent to 10,000 Suns burning at once.

Dancing jet technique

Cygnus X-1 is a high-mass X-ray binary system and the first celestial object widely confirmed to be a black hole. 

It consists of a stellar-mass black hole — about 21 times the mass of the Sun — locked in a tight orbit with a massive supergiant star. 

As the black hole’s gravity strips material from its companion, the gas forms a glowing accretion disk that emits intense X-rays and powers relativistic jets traveling at extreme speeds. 

Famously the subject of a friendly wager between Stephen Hawking and Kip Thorne, the system remains a natural laboratory for studying the extreme physics of gravity and galactic evolution.

However, measuring something thousands of light-years away is rarely straightforward.

To do it, lead author Dr. Steve Prabu and his team turned to a “telescope the size of the Earth” — an array of linked dishes spanning vast distances. 

It enabled the capture of a sequence of images showing the jets being buffeted. As the black hole moves through its orbit, these winds slam into its jets, pushing and bending them.

The power of the jets was determined by measuring the degree of their deflection caused by the wind from the nearby star.

Anchoring the universe

Astronomers and physicists mostly build massive computer simulations to understand how the universe grew. 

These models rely on a specific assumption: that 10% of the energy released by matter falling into a black hole is emitted as jets.

Until now, the “10% rule” was mostly an educated guess.

“We can now use this measurement to anchor our understanding of jets, whether they are from black holes 10 or 10 million times the mass of the Sun,” said co-author Professor James Miller-Jones. 

Whether a black hole is ten times the mass of the Sun or ten million, the physics appears to be the same. The data confirmed that the 10% efficiency used in simulations is remarkably accurate.

Black hole jets are the architects of the cosmos. The jets pump energy into the gas between stars and prevent new stars from forming too quickly, thereby regulating the growth of entire galaxies.

With the Square Kilometer Array (SKA) currently under construction in Western Australia, astronomers will soon be able to see millions of these jets across the distant reaches of space. 

Thanks to the “dancing jets” of Cygnus X-1, experts now have the perfect ruler to measure them.

This development enables direct comparison of the jet’s output with the immediate X-ray energy released by matter falling into the black hole, providing a far more accurate picture of how these cosmic engines operate.

The findings were published in the journal Nature Astronomy on April 16.