Back in April 2019, the Event Horizon Telescope (EHT) Collaboration revealed the first-ever direct image of a black hole. The image of the black hole, named M87*, showed the object’s shadow, as well as its ring of glowing matter. Now, EHT researchers say that M87*’s ring is also wobbling around its shadow. This huge discovery could yield important insights about the laws of physics.
Can you wobble? The M87 black hole does!— National Science Foundation (@NSF) September 23, 2020
The @ehtelescope debuted the first #realblackhole image in 2019, but with NSF support, it was gathering data long before that. This data showed that the "shadow" of the M87 black hole wobbles over time: https://t.co/qoCbqWqHtA pic.twitter.com/oU9ba5J07B
The EHT simulation of M87* in the above tweet shows how its ring wobbles. The simulation takes place over one year and shows super-hot matter moving around M87*’s shadow. For reference, a black hole’s shadow is the part of the object where light has not escaped its gravitational pull. Photons from hot, radiating gas swirling around the black hole’s event horizon compose the crescent ring of light.
“Because the flow of matter falling onto a black hole is turbulent, we can see that the ring wobbles with time,” said Maciek Wielgus in a press release (via Gizmodo). Wielgus, an astronomer at Harvard who led the EHT team, initially wanted to study M87*’s general morphology. To his and his colleagues’ surprise, they found that the ring around the supermassive black hole—which sits at the center of the Messier 87 galaxy—wobbles.
M. Wielgus, D. Pesce/Event Horizon Telescope
“In 2019, we saw the shadow of a black hole for the first time, but we only saw images observed during a one-week window, which is too short to see a lot of changes,” Wielgus noted. To develop a better understanding of how M87* changes over time, Wielgus et al. studied data collected by EHT. (EHT is a global network of observatories working in unison to observe radio sources associated with black holes.) The team analyzed data from EHT collected on M87* from 2009, and 2011 through 2013.
Although the team had observational data on M87* from those four years, it didn’t have enough to develop direct images. Instead, the team used statistical modeling to look for changes in the appearance of M87* over time. In a paper recently published in The Astrophysical Journal, the team describes how it compared the EHT observational data to geometric templates—in this case rings of non-uniform brightness—and determined which template was most consistent.
European Southern Observatory
“The dynamics of this wobbling will allow us to constrain the accretion flow,” Richard Anantua, said in the press release. Anantua, a postdoc at Harvard involved in the research, explained, “The accretion flow contains matter [that] gets close enough to the black hole to allow us to observe the effects of strong gravity, and in some circumstances, allows us to test predictions from general relativity….”
In fact, the position and angle measurements of M87* taken by the team have already yielded insights. Namely that variations in the supermassive black hole’s morphology are in “broad agreement” with predictions made by General Relativity. “If you want to see a black hole evolve over a decade, there is no substitute for having a decade of data.” Wielgus said. The astronomer added that more observations “will lead to a better understanding of the dynamical properties of M87” and black holes in general.
Featured Image: European Southern Observatory