Black holes rank among the universe’s most extreme entities, capable of ejecting material at nearly light speed through powerful plasma beams known as jets. These jets are considered some of the cosmos’ most energetic occurrences.
Our recent study, published today in Nature Astronomy, questions this belief. We discovered that the “wind” from a star, which seems quite ordinary, can compete with and even influence these mighty jets.
A cosmic waltz
The Cygnus X-1 system represents a cosmic dance between a black hole and a massive star.
This black hole, the first ever found, has a mass approximately 21 times that of our Sun, condensed into a space about 100 kilometers wide.
It exists in a binary system with a companion star nearly 40 times the Sun’s mass. The black hole and star complete an orbit around each other every 5.6 days.
For around 20,000 years, the black hole has been consuming material from this star by capturing its potent stellar wind through its strong gravitational force.
Some of this material vanishes into the black hole, crossing the event horizon in a one-way trip. The magnetic fields that swirl with the ingested gas generate jets that travel at nearly the speed of light.
These jets transport energy from the black hole to a distance a trillion times greater, reaching 16 light-years away.
Over the last 20,000 years, they have expanded a vast bubble of hot gas in the surrounding interstellar space. Despite their significance, accurately measuring the real-time power of these jets has been a significant obstacle until now.
The power couple
Stellar winds are streams of particles propelled off a star’s surface by the outward pressure of light. When the solar wind from our Sun intensifies, it results in auroras as particles collide with Earth’s magnetic field.
The massive and bright companion star in Cygnus X-1 loses mass through its wind at a rate 100 million times greater than the Sun, accelerating to speeds three times faster.
In our research, we created highly detailed images of the jets by combining data from telescopes thousands of kilometers apart. This technique was also utilized by the Event Horizon Telescope to capture the first image of a black hole.
We observed that the wind from the Cygnus X-1 companion star is powerful enough to bend the black hole’s jets, highlighting the formidable strength of massive stars’ winds.
As the black hole revolves around the star, the stellar wind persistently pushes against the jets, diverting them from the star. This causes the jets to shift direction, similar to how wind on Earth can redirect water in a fountain.
From our perspective, the jets appear to “dance” in sync with the system’s orbital movement. By analyzing this cosmic dance, we were able to measure the jets’ instantaneous power for the first time, finding it equivalent to the energy of 10,000 suns.
The calorie deficit of a black hole diet
Understanding how black holes utilize their energy is crucial for grasping galaxy evolution.
As matter approaches a black hole, part of it contributes to the black hole’s growth, while a significant portion can be expelled into jets, returning energy to the surroundings.
The jets from the most massive black holes at galaxy centers can shape their host galaxies and influence even larger cosmic structures.
We can gauge a black hole’s feeding rate through the X-rays emitted by incoming material. Until now, however, there was no direct method to measure the energy channeled into jets at any moment.
Our measurement of the jet power in Cygnus X-1 offers a new means to “balance the energy budget” of black holes.
By comparing a black hole’s feeding rate with the energy carried away by jets, we can refine computer simulations of the universe, enhancing our understanding of how black holes impact the universe on a grand scale.
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This cosmic choreography of a black hole and a massive star uncovers more than just a bent jet. It illustrates how even the most energetic phenomena, like jets, are influenced by their environment.
By observing the dancing jets in Cygnus X-1, we have gained deeper insights into how black holes shape the evolution of the cosmos itself.
Steve Prabu, Adjunct Lecturer, School of Electrical Engineering, Computing and Mathematical Sciences, Curtin University; University of Oxford and James Miller-Jones, Professor, Curtin Institute of Radio Astronomy, Curtin University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
