Black Hole Jet Power Measured for the First Time | Cygnus X-1 Carries Energy of 10,000 Suns

Astronomers have made the first direct measurement of the instantaneous power of jets shooting from a black hole, finding they carry energy equivalent to 10,000 suns and travel at approximately half the speed of light. The findings, published in Nature Astronomy, confirm a long-held assumption at the foundation of models describing how galaxies evolve across cosmic time, placing a hard observational number on a process previously estimated only indirectly.

The black hole in question is Cygnus X-1, located about 7,200 light-years from Earth and notable as the first black hole ever confirmed by scientists. The system pairs the black hole with a massive supergiant companion star, and it is this pairing that made the measurement possible.

18 Years of Radio Imaging | Jets Bent by Stellar Wind

The research was led by Dr. Steve Prabu, now based at the University of Oxford, working through Curtin University's Institute of Radio Astronomy. The team linked radio telescopes across the globe to build 18 years of high-resolution imaging of Cygnus X-1's jets, capturing unprecedented detail in how the jets behave as the black hole and companion star orbit one another.

What they observed was the jets being repeatedly deflected, or “dancing,” in Dr. Prabu's description, pushed in different directions by the powerful stellar winds blowing off the companion star. The analogy he offered is intuitive: strong winds on Earth pushing water sideways from a fountain. By precisely measuring the degree to which the jets bent and combining that with independent knowledge of the stellar wind's power, the team was able to calculate the jets' kinetic energy for the first time directly rather than by inference.

The Measurement | 150,000 km/s, Energy of 10,000 Suns

The jets travel at approximately 150,000 kilometers per second, just under half the speed of light at roughly 299,792 km/s. Their instantaneous kinetic power is equivalent to the combined energy output of 10,000 stars like the Sun. Both figures had been estimated in prior theoretical work, but this is the first time observational data has directly confirmed the numbers, giving astrophysicists a calibration point they have been working toward for decades.

The significance extends beyond Cygnus X-1 itself. Jets from black holes are believed to be one of the primary mechanisms by which black holes regulate star formation in their host galaxies, injecting energy into surrounding gas and suppressing or triggering new stellar growth depending on conditions. The models that describe this galaxy-scale feedback process have until now relied on assumed jet power values. A direct measurement makes those models substantially more reliable and opens a new observational pathway for studying black holes across cosmic distances.

Galaxy Evolution | Why Jet Power Matters at Scale

The broader implication of the Cygnus X-1 measurement is a more accurate picture of how energy flows from black holes into galaxies over billions of years. Supermassive black holes at galactic centers produce jets orders of magnitude more powerful than those of Cygnus X-1, and the same physical principles governing the stellar-mass system apply at larger scales. By establishing the measurement method in a nearby, well-characterized system, the Curtin team has provided a template that can be extended to more distant and energetic objects as radio telescope networks continue to improve in resolution and sensitivity.