Astronomers analyzing M87*, the first black hole ever imaged, have discovered that its shadow changes from year to year. The latest observations from the Event Horizon Telescope (EHT) confirm that the black hole’s appearance evolves over time due to turbulence in its surrounding gas.

The Changing Shadow of M87*

In 2019, the EHT collaboration released the first-ever image of a black hole, a “fiery doughnut” showing the shadow of M87*, a supermassive black hole located 55 million light-years away.

This shadow is caused by the intense gravitational bending of light around the black hole’s event horizon, and its size helps estimate the black hole’s mass, which is about 6.5 billion times that of the Sun.

However, when researchers compared the 2017 and 2018 EHT observations, they noticed something unexpected: the bright ring surrounding the shadow had shifted.

What Causes The Shifting Image?

The changes in M87*’s shadow are linked to the extreme and dynamic nature of its accretion disc, the swirling mass of gas and matter being pulled toward the event horizon object. This disc generates immense amounts of light and energy, influenced by magnetic fields and relativistic effects.

The EHT team applied Bayesian statistical analysis to compare the 2017 and 2018 images, treating them as independent observations. They found that the bright ring’s location fluctuates due to turbulence in the hot gas surrounding the dark vortex.

These fluctuations occur because matter around the black hole moves chaotically, influenced by its strong gravity and magnetic fields.

The Orientation of M87* And Its Spinning Jets

The bright ring in the EHT images is not uniform; one side appears brighter due to the relativistic motion of material in the accretion disc, which is moving close to the speed of light.

In the 2017 image, the brightest part was slightly off from predictions, but by 2018, it had returned to its expected position, supporting previous theoretical models of how matter behaves near black holes.

These findings published in Astronomy & Astrophysics also connect to another major discovery about M87*: its powerful jets of plasma, which extend thousands of light-years into space. In 2021, the EHT team analyzed the polarization of light around M87* and found evidence of highly magnetized gas.

Observing Black Holes with Earth-sized Telescopes

Studying black holes at such high resolution requires a network of radio telescopes spanning the globe. The EHT uses a technique called very long baseline interferometry (VLBI), which links observatories across North America, South America, Europe, Antarctica, and Asia.

This effectively creates a virtual telescope the size of Earth, allowing scientists to resolve details as small as tens of micro-arcseconds, equivalent to seeing a coin on the Moon from Earth.

Key facilities involved in this research include the Atacama Large Millimeter Array (ALMA) in Chile, the South Pole Telescope (SPT) in Antarctica, and the James Clerk Maxwell Telescope (JCMT) in Hawaii.

The data collected from these telescopes is combined and processed at institutions such as the Max-Planck-Institut für Radioastronomie in Germany and the MIT Haystack Observatory in the United States.

What’s Next for Black Hole Research?

The EHT team is now analyzing observations from 2021 and 2022, aiming to further refine models of black hole accretion. Future studies will focus on how the polarization of light changes over time, providing even deeper insights into strong gravity, magnetized plasma, and jet formation near black holes.