FAQ

How long did it take to make an image of a black hole?

Observational campaigns in both April 2017 and April 2018 were conducted over five observing nights. These data were recorded when the major target sources were optimally observable by night and when the weather was globally best for EHT observations. Each telescope observed EHT targets and various celestial calibrators for approximately 8 hours per night.

However, the EHT collaboration effort has been evolving over more than 20 years and continues to go forward. Such a daring endeavor required developing new hardware and software throughout this period and especially in the...

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How many researchers contributed to making of the first black hole image?

The Event Horizon Telescope (EHT) Collaboration is a team of two hundred individual researchers situated at a number of research institutions around the world. The EHT is subdivided into different expert teams to address the different challenges of the coordinating a global research effort, such as phasing individual arrays to work as a single telescope of the global network, outfitting the telescopes at the different sites with new hardware and software...

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How realistic are movie depictions of black holes, for example in the "Interstellar"?

The portrayal of the black hole "Gargantua" in the movie Interstellar  is somewhat realistic, in that they show the general morphology of these cosmic structures accurately. However, for aesthetic reasons, the movie producers removed one important aspect of the imaging to make the black hole more dramatic: the Doppler effect is switched off in the movie. In reality, the approaching side of the rotating accretion disk would appear brighter and hotter (blueish white), while the receding side would be dimmer and more red. Although the Interstellar production team consulted...

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How many telescopes are currently in the EHT network?

The EHT is an evolving network of telescopes. Observations in April 2017 were carried out with eight observatories in six geographical locations around the globe. For the observing campaign in 2018, one new telescope was added to the array, totalling nine observatories at seven sites.

No observations with the EHT array were performed in 2019 and 2020. We plan to add additional observatories to the array for future observational campaigns -- two more are expected to join the array for observations in 2021, totalling eleven observatories at nine different locations around the...

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Can we really photograph a black hole? Are they not entirely dark, since no light can escape them?

The first image of a black hole is not a classical photograph. It is a radiolight image the result of complex observational and computational interpretation (deconvolution). Further, it is not of the black hole itself, but of the "shadow"—the closest we can come to imaging a completely dark object that consumes all light and matter. The black hole boundary—the event horizon for which the EHT is named—casts this shadow. General Relativity says the superheated material around the black hole will glow and illuminate the strongly warped region of spacetime, making it visible to...

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