4 ms·

For anyone curious, some years ago I talked with the NSO outreach folks, and they were aware then that the Sun is white, and that yellow/orange is a misconcepti

For anyone curious, some years ago I talked with the NSO outreach folks, and they were aware then that the Sun is white, and that yellow/orange is a misconception widespread and problematic in both astronomy education and the general US population, and that their colorizations were not helping with that. Their justification was roughly that you need to hook people with what they expect, and only then can you make progress with educating them. I thought and think that that's very much the wrong call, as well as over the line ethically, but... oh well. Though the misconception really is pervasively widespread, even among first-tier astronomy graduate students, so perhaps there might now be a degree of confusion present as well. And a (very) few instances of colorization are representationally valid, if unfortunate in their collateral damage, as when representing that some instrument's sampling band is in yellow.

mturmon 7y ago
You have mentioned a neat point that illustrates some of the complexity of an "image" like the ones shown. After 20 or so minutes poking around, I'm not 100% sure what instrument took the images in the OP. There are five focal planes that can get the light from this much-anticipated solar telescope, which has been envisioned and prototyped going back at least 20 years. Anyway, I think the instrument for the images was VBI, the Visible Broadband Imager (https://www.nso.edu/telescopes/dkist/instruments/vbi/ https://www.nso.edu/telescopes/dkist/instruments/vbi/). It takes images in 8 spectral bands, in the visible range. But these bands are very narrow, like 0.5nm or less. (Solar astronomy is cool that way, lots of photons of whatever energy you want.) The specific bands have been carefully selected. One band that page calls call "continuum" (sometimes referred to as "pseudo-white-light", found in the "spectral resolution" submenu) is at 450nm, in the blue. All the 8 various bands illustrate activity at different altitudes in the solar atmosphere. The 450nm band will be from the solar photosphere, where sunspots and other familiar features live. Some others are much higher up, and sunspots will not be present as such in those bands. If this conjecture is true, the displayed images are taken in a very narrow slice of spectrum around 450nm (or another one around 668nm, which is in red) and then mapped through a black/orange/yellow/white color map for display. This kind of "colorization" is pervasive throughout solar astronomy, and used universally by astronomers themselves for their own science images. (Visit https://umbra.nascom.nasa.gov/newsite/images.html https://umbra.nascom.nasa.gov/newsite/images.html and weep.) As hinted in your last sentence, it's not at all clear what a "correct" colormap for light from 450nm +/- 0.5nm should be. Shades of blue? For more on your point: http://solar-center.stanford.edu/SID/activities/GreenSun.html http://solar-center.stanford.edu/SID/activities/GreenSun.htm... (old-fashioned site, but technically 100% solid).
- lolc 7y ago
  The source article[0] linked in another thread says the images are of the 789nm band. [0] https://www.nso.edu/inouye-solar-telescope-first-light/ https://www.nso.edu/inouye-solar-telescope-first-light/
BurningFrog 7y ago
Our vision is evolutionarily adapted to sunlight, so it makes all the sense that sunlight should be perceived as neutral white.
- finnh 7y ago
  But we perceive it as yellow ... it's only white if you are outside the atmosphere, a condition to which we are not evolutionarily adapted.
SiempreViernes 7y ago
The sun is not white, it actually is a lot of different colours that then happen to look white. White is anyway a rather difficult colour to use as base if you want to show any detail. The importance of your "misconception" is unclear to me, most people have seen the sun for themselves (though I expect all have been told not to look) and can tell the difference between the real thing and a picture of it.
- radarsat1 7y ago
  > a lot of different colours that then happen to look white. Seeing as white is just "full spectrum", that is literally just the definition of white. So yes, the sun is white.
  - xorcist 7y ago
    But it's not (evenly) full spectrum though, so why would it be white? I can understand either green (the blackbody peak) or red/yellow (as seen with human eyes through our atmosphere). Who would considered it white, apart from an astronaut?
raxxorrax 7y ago
I think the sun is green, since its spectrum clearly peaks at those wavelengths. But if I tell that to anyone they often suggest I should go to sleep again. G-class stars like the sun are called yellow dwarfs, which is also inaccurate.
- freeflight 7y ago
  I wonder how much of these disagreements are based on the individually different perception of colors [0]? [0] https://en.wikipedia.org/wiki/The_dress https://en.wikipedia.org/wiki/The_dress
  - sand500 7y ago
    I don't think the dress is a good example of different people perceiving colors differently since individuals can see it both ways.
bregma 7y ago
> ... the misconception really is pervasively widespread, even among first-tier astronomy graduate students ... Even first-year undergraduate astronomy students dont't think a star "is a colour" considering the useful information when dealing withs come from spectra, not photos. Stellar classification on an H-R diagram is a convenience, that is all. It's already acknowledging "colour shift" from the Doppler effect (aka "red shifting"), but every first-year astronomy undergrad knows no two stellar spectra are the same, none are a single wavelength, and "white light" is a perceptual phenomenon not a physical one.
api 7y ago
Reminds me of the minor controversy around the color of the Mars sky. Turns out that replicating perceptual color as it would be experienced by a person standing on another body or looking directly at it is not really that simple. Cameras designed for use on Earth are calibrated for a certain environment and even then you can get differences in how colors show up or are perceived on photos. Turns out a person on Mars would sometimes see a bluish sky depending on how much suspended dust is present, the altitude, and the time of day.

mturmon 7y ago

You have mentioned a neat point that illustrates some of the complexity of an "image" like the ones shown. After 20 or so minutes poking around, I'm not 100% sure what instrument took the images in the OP. There are five focal planes that can get the light from this much-anticipated solar telescope, which has been envisioned and prototyped going back at least 20 years. Anyway, I think the instrument for the images was VBI, the Visible Broadband Imager (https://www.nso.edu/telescopes/dkist/instruments/vbi/ https://www.nso.edu/telescopes/dkist/instruments/vbi/). It takes images in 8 spectral bands, in the visible range. But these bands are very narrow, like 0.5nm or less. (Solar astronomy is cool that way, lots of photons of whatever energy you want.) The specific bands have been carefully selected. One band that page calls call "continuum" (sometimes referred to as "pseudo-white-light", found in the "spectral resolution" submenu) is at 450nm, in the blue. All the 8 various bands illustrate activity at different altitudes in the solar atmosphere. The 450nm band will be from the solar photosphere, where sunspots and other familiar features live. Some others are much higher up, and sunspots will not be present as such in those bands. If this conjecture is true, the displayed images are taken in a very narrow slice of spectrum around 450nm (or another one around 668nm, which is in red) and then mapped through a black/orange/yellow/white color map for display. This kind of "colorization" is pervasive throughout solar astronomy, and used universally by astronomers themselves for their own science images. (Visit https://umbra.nascom.nasa.gov/newsite/images.html https://umbra.nascom.nasa.gov/newsite/images.html and weep.) As hinted in your last sentence, it's not at all clear what a "correct" colormap for light from 450nm +/- 0.5nm should be. Shades of blue? For more on your point: http://solar-center.stanford.edu/SID/activities/GreenSun.html http://solar-center.stanford.edu/SID/activities/GreenSun.htm... (old-fashioned site, but technically 100% solid).

lolc 7y ago
The source article[0] linked in another thread says the images are of the 789nm band. [0] https://www.nso.edu/inouye-solar-telescope-first-light/ https://www.nso.edu/inouye-solar-telescope-first-light/

BurningFrog 7y ago

Our vision is evolutionarily adapted to sunlight, so it makes all the sense that sunlight should be perceived as neutral white.

finnh 7y ago
But we perceive it as yellow ... it's only white if you are outside the atmosphere, a condition to which we are not evolutionarily adapted.

SiempreViernes 7y ago

The sun is not white, it actually is a lot of different colours that then happen to look white. White is anyway a rather difficult colour to use as base if you want to show any detail. The importance of your "misconception" is unclear to me, most people have seen the sun for themselves (though I expect all have been told not to look) and can tell the difference between the real thing and a picture of it.

radarsat1 7y ago
> a lot of different colours that then happen to look white. Seeing as white is just "full spectrum", that is literally just the definition of white. So yes, the sun is white.
- xorcist 7y ago
  But it's not (evenly) full spectrum though, so why would it be white? I can understand either green (the blackbody peak) or red/yellow (as seen with human eyes through our atmosphere). Who would considered it white, apart from an astronaut?

raxxorrax 7y ago

I think the sun is green, since its spectrum clearly peaks at those wavelengths. But if I tell that to anyone they often suggest I should go to sleep again. G-class stars like the sun are called yellow dwarfs, which is also inaccurate.

freeflight 7y ago
I wonder how much of these disagreements are based on the individually different perception of colors [0]? [0] https://en.wikipedia.org/wiki/The_dress https://en.wikipedia.org/wiki/The_dress
- sand500 7y ago
  I don't think the dress is a good example of different people perceiving colors differently since individuals can see it both ways.

bregma 7y ago

> ... the misconception really is pervasively widespread, even among first-tier astronomy graduate students ... Even first-year undergraduate astronomy students dont't think a star "is a colour" considering the useful information when dealing withs come from spectra, not photos. Stellar classification on an H-R diagram is a convenience, that is all. It's already acknowledging "colour shift" from the Doppler effect (aka "red shifting"), but every first-year astronomy undergrad knows no two stellar spectra are the same, none are a single wavelength, and "white light" is a perceptual phenomenon not a physical one.

api 7y ago

Reminds me of the minor controversy around the color of the Mars sky. Turns out that replicating perceptual color as it would be experienced by a person standing on another body or looking directly at it is not really that simple. Cameras designed for use on Earth are calibrated for a certain environment and even then you can get differences in how colors show up or are perceived on photos. Turns out a person on Mars would sometimes see a bluish sky depending on how much suspended dust is present, the altitude, and the time of day.