The first-ever image of a black hole released this week was taken with radio telescopes, suggesting that it is a false-color image and doesn't represent what a person would see in reality, or visible light. This seems to be confirmed by this Wired article, but I am perplexed as to why this is not widely mentioned, including the announcement on the telescope's official website and Wikipedia (image file, article on black holes). Perhaps not mentioning it makes for better headlines, but it feels wrong.
What's going on here?
Answer
Yes, it's a false-color image. Radio telescopes don't detect visible light.
In the first of the six technical papers (which seem to be open access! they are listed in this summary article), the color scale is assigned a physical interpretation:
The interpretation is at the bottom: it's some kind of an effective temperature, with dark being "cold" and the brightest being six billion kelvin. There's a huge amount of detail in the technical papers.
I decline to speculate on why news organizations do or don't say things. But it sure is less confusing to look at false-color images that use modern perceptually-uniform color mappings.
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