10 Deep Lessons From Our First Image Of A Black Hole’s Event Horizon
“6. Black holes are dynamic entities, and the radiation emitted from them changes over time. With a reconstructed mass of 6.5 billion solar masses, it takes roughly a day for light to travel across the black hole’s event horizon. This roughly sets the timescale over which we expect to see features change and fluctuate in the radiation observed by the Event Horizon Telescope.
Even with observations that span only a few days, we’ve confirmed that the structure of the emitted radiation changes over time, as predicted. The 2017 data contains four nights of observations. Even glancing at these four images, you can visually see how the first two dates have similar features, and the latter two dates have similar features, but there are definitive changes that are visible — and variable — between the early and late image sets. In other words, the features of the radiation from around M87’s black hole really are changing over time.”
I’ve heard some grumbling over the past day that people are unimpressed with the Event Horizon Telescope collaboration’s big reveal. Maybe the image doesn’t look pretty enough for some people; maybe it doesn’t have the sharpness or level of detail that people are used to from observatories like Hubble.