For the first time, astronomers have directly measured the staggering velocity of a particle jet erupting from a black hole, clocking it at 99.5 percent of the speed of light. The discovery, made using a continent-wide radio telescope in Australia, reveals a cosmic engine of almost incomprehensible power.
## The Relativistic Cannon in the Sky
## A Telescope the Size of a Continent
## Why This Measurement Matters
The phenomenon originates from a binary star system named MAXI J1820+070, located roughly 10,000 light-years from Earth. This system contains a stellar-mass black hole, a remnant of a collapsed star, which is actively pulling material from a companion star. As this stolen gas spirals inward, it forms a superheated disk. From the poles of this disk, the black hole launches twin beams, or jets, of subatomic particles into the void. These jets are a fundamental feature of black holes, but their precise mechanics have remained elusive.
To solve this, an international team led by Australian researchers turned to the Australian Square Kilometre Array Pathfinder (ASKAP), a network of 36 dish antennas spread across hundreds of kilometers in Western Australia. By combining their signals, ASKAP acts as a single, continent-sized eye. In April 2022, they detected a sudden, powerful flare from the jets of MAXI J1820+070. Crucially, they observed a time delay between the arrival of light from the base of the jet and a bright knot of material further out. This delay, a mere 52 milliseconds, allowed them to perform a cosmic speed trap calculation.
The result was a direct measurement of the jet's bulk velocity: 299,537 kilometers per second, or 99.5 percent of light speed. The team also calculated the jet's kinetic power, finding it rivals the total radiant power emitted by the entire accretion disk. This means the black hole channels as much energy into hurling particles into deep space as it does into generating the brilliant light from its immediate surroundings. The finding provides the first concrete benchmark for theoretical models of how black holes convert gravitational energy into these focused beams.
This landmark measurement offers a new empirical foundation for astrophysics. By confirming the extreme velocities and immense power of these relativistic jets, scientists now have a critical data point to understand one of the universe's most efficient and violent engines. It demonstrates that the energy channeled into these narrow beams is a dominant, and previously under-quantified, output of a feeding black hole, reshaping our comprehension of how these objects interact with and influence their galactic environments.
