First Direct Measurement of a Black Hole's Instantaneous Jet Power
An international research team has, for the first time, directly measured the instantaneous power of relativistic jets emitted by a black hole. Using a global array of radio telescopes, the team observed the black hole in the Cygnus X-1 system and determined its jets have a power output equivalent to 10,000 Suns and travel at approximately half the speed of light. The findings, published in Nature Astronomy, provide a new benchmark for calibrating models of black hole behavior and galaxy evolution.
The instantaneous power of the jets was measured to be approximately 10,000 times the total power output of the Sun.
The System and Measurement
The research focused on the Cygnus X-1 system, located approximately 7,200 light-years from Earth. The system consists of a stellar-mass black hole, the first such object ever confirmed, and a supergiant companion star.
The key measurement was achieved by observing how the powerful stellar winds from the supergiant star deflected the black hole's jets as the two objects orbited each other. By precisely measuring the degree of this bending and knowing the power of the stellar wind, the research team calculated the instantaneous power required for the jets to resist the wind force.
Key Findings
- Jet Power: The instantaneous power of the jets was measured to be approximately 10,000 times the total power output of the Sun.
- Jet Speed: The jets were measured to travel at a speed of about 150,000 kilometers per second, roughly half the speed of light.
- Energy Fraction: The measurement indicates that roughly 10% of the gravitational energy released as matter falls toward the black hole is channeled into powering these jets.
Methodological Significance
Previous methods for estimating black hole jet power could only provide an average over thousands or millions of years. The new technique marks the first time researchers have been able to measure the jet power at a specific moment in time.
According to the study's lead author, Dr. Steve Prabu, this finding observationally confirms an assumption about energy conversion that is commonly used in large-scale simulated models of the universe.
Co-author Professor James Miller-Jones stated that the ability to measure instantaneous power allows for a direct comparison with the simultaneous X-ray emission from the infalling matter, which was not possible with previous averaged measurements.
Research Context and Implications
The physics governing jet formation is theorized to be similar for black holes of all masses. Therefore, the researchers state that this precise measurement from a nearby stellar-mass black hole can serve as an "anchor point" or reference for understanding the behavior and impact of jets from supermassive black holes, which can be millions of times more massive.
Black hole jets are considered a critical form of "feedback," depositing enormous energy into their surrounding environments and influencing the rate of star formation and the evolution of galaxies.
Future Applications
The research team noted that upcoming radio telescope projects, specifically the Square Kilometre Array Observatory (SKAO), are designed to detect jets from millions of black holes in distant galaxies. The calibration provided by this study will help astronomers accurately determine the power output of those distant jets, enhancing our understanding of black hole growth and galactic evolution across cosmic time.
Publication and Collaboration
The research paper, titled 'A jet bent by a stellar wind in the black hole X-ray binary Cygnus X-1', was published in the journal Nature Astronomy.
The study was led by researchers from the Curtin Institute of Radio Astronomy (CIRA) and the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR). The collaboration included scientists from:
- University of Oxford
- University of Barcelona
- University of Wisconsin-Madison
- University of Lethbridge
- Institute of Space Science