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How is the “Picture” of the Sagittarius A* Black Hole Made From Radio Telescope Observations?

-- Kelly | May 13, 2022

Question:

Today’s announcement (12 May) of a ‘picture’ taken by the Event Horizon Telescope is confusing. Help. It is claimed that a picture has been taken of Sagittarius A*. But that is a radio telescope? So, the ‘image’ isn’t really an image is it? Seems someone took the radio wavelengths and just transposed them to visible light wavelengths? Why is everyone calling this an image?

-- Kelly

Answer:

By combining the signals from multiple telescopes radio astronomers are able to produce images or “pictures”, such as the newly-released image of the black hole at the center of our Galaxy. Details can be found in a previous answer to the question of how a radio interferometer works.

-- Jeff Mangum

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