For the first time, astronomers were able to map the magnetic-field structure extremely close to a black hole by studying the polarization of light around M87* — the supermassive black hole that became famous as the first black hole ever imaged. The breakthrough offers a remarkable glimpse into how black holes can power enormous jets that blast material across thousands of light-years.
🌌 A New View of M87*
At the heart of the giant elliptical galaxy Messier 87, about 55 million light-years from Earth, lies M87*, a black hole with a mass roughly 6.5 billion times that of the Sun.
In 2019, the Event Horizon Telescope (EHT) revealed its iconic glowing ring surrounding a dark central shadow. But the original image showed mainly the distribution of radio emission. The next question was far more ambitious: What is happening to the magnetic fields in this extreme environment?
The answer came through polarized light.
🧲 Reading Magnetic Fields Through Light
Light can become polarized when it travels through magnetized plasma. By measuring the polarization pattern of the radiation surrounding M87*, scientists could infer the structure of the magnetic fields threading the region near the event horizon.
🔹 The EHT observed M87* at a wavelength of about 1.3 millimetres.
🔹 The polarization pattern showed an organized, nearly azimuthal structure around the black hole.
🔹 Researchers found evidence consistent with strong, organized magnetic fields close to the event horizon.
🔹 Models indicate magnetic fields in the emitting plasma could be on the order of 1–30 gauss, depending on the model used.
This is crucial because the magnetic field is not simply a passive feature. It may be one of the mechanisms controlling how matter falls toward the black hole — and how some of that matter is redirected outward.
⚡ The Cosmic Engine Behind Giant Jets
M87* produces one of astronomy’s most spectacular phenomena: a relativistic jet of particles and energy emerging from its central region.
These jets extend at least 5,000 light-years from M87’s centre.
🔹 Powerful magnetic fields can become tightly wound around the rotating black hole and surrounding accretion flow.
🔹 The magnetic structure can help channel plasma away from the immediate surroundings of the black hole.
🔹 Some theoretical models suggest a magnetically arrested accretion disk, where magnetic fields become dynamically important, can help explain the observed jet power.
The result is almost paradoxical: a region famous for swallowing matter can also help launch some of the most powerful outflows in the universe.
đź” Why This Discovery Matters
This achievement goes beyond producing another spectacular black-hole image. It gives scientists a new experimental window into the physics operating in one of the most extreme environments known.
The observations help connect the tiny region immediately surrounding a black hole with a jet thousands of light-years long — essentially linking the black hole’s immediate environment to its enormous cosmic impact.
And the story is still evolving. Later observations have shown that the polarisation and magnetic environment of M87* can change over time, suggesting that this cosmic engine is far from static.Â
M87* is teaching astronomers that black holes are not merely cosmic vacuum cleaners. Their magnetic environments can act as engines, channels and launchpads — transforming matter and magnetic energy into enormous jets that reshape their surroundings.
What once looked like a mysterious glowing ring is becoming a detailed map of a cosmic machine.
One black hole. One magnetic field. Thousands of light-years of consequences.
