First-Ever Photographed Black Hole Shows Dramatic Changes In Follow-Up Observations

The image of M87*, the supermassive black hole at the center of massive elliptical galaxy M87, changed the world. It was the first-ever direct image of a black hole, showing the gargantuan object’s shadow and the light present at the edge of it. The observations were taken in 2017 by the Event Horizon Telescope (EHT) and there have been follow-ups ever since. Now, the EHT has shown that a year after the iconic photo, M87* had changed.

In the 12 months between observations, the brightest region around the supermassive black hole has shifted. This confirms that there is turbulence in the accretion disk – the rotating gas around the black hole is not experiencing a smooth flow. It also provides new insights into the black hole compared to the first observations alone.  

“The black hole accretion environment is turbulent and dynamic. Since we can treat the 2017 and 2018 observations as independent measurements, we can constrain the black hole’s surroundings with a new perspective,” EHT member Hung-Yi Pu, assistant professor at National Taiwan Normal University, said in a statement. “This work highlights the transformative potential of observing the black hole environment evolving in time.”

M87* weighs 6.5 billion times our Sun. It’s over 1,000 times heavier than Sagittarius A*, the black hole at the center of the Milky Way. The 2018 observation confirms a lot of what was seen in 2017, but it is clear to see that the brightest region has shifted by 30 degrees counterclockwise, as was predicted.

“The shift in the brightest region is a natural consequence of turbulence in the accretion disk around the black hole,” explained Abhishek Joshi, a PhD candidate at the University of Illinois Urbana-Champaign. “In our original theoretical interpretation of the 2017 observations, we predicted that the brightest region would most likely shift in the counterclockwise direction. We are very happy to see that the observations in 2018 confirmed this prediction!”

From the original observations, the team made several predictions beyond the shift, further confirming hypotheses put forward after the first series of observations.  

“The location of the brightest region in 2018 also reinforces our previous interpretation of the black hole’s orientation from the 2017 observations: the black hole’s rotational axis is pointing away from Earth!” Bidisha Bandyopadhyay, a Postdoctoral Fellow from Universidad de Concepción, added.

The team also further explored computer models to better understand this black hole and all supermassive black holes, especially the active ones such as M87*. What we learn here, is applicable far beyond.

“When gas spirals into a black hole from afar, it can either flow in the same direction the black hole is rotating, or in the opposite direction. We found that the latter case is more likely to match the multi-year observations thanks to their relatively higher turbulent variability,” explained León Sosapanta Salas, a PhD candidate at the University of Amsterdam. 

“Analysis of the EHT data for M87 from later years (2021 and 2022) is already underway and promises to provide even more robust statistical constraints and deeper insights into the nature of the turbulent flow surrounding the black hole of M87.”

The findings are published in the journal Astronomy & Astrophysics.

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