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Thread: Visual star colors

  1. #1
    Join Date
    Mar 2004
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    Visual star colors

    (paging George!)

    Since it comes up - here's some new work carefully assigning RGB components to star colors of various temperature, using proper model atmospheres instead of blackbody approximations. Among many other things, they get above-atmosphere RGB components (1, 0.931, 0.905) for a main-sequence star at the Sun's temperature, which is pretty neutral. Red dwarfs aren't really red and white dwarfs are not always white.

    Digital color codes of stars, by Jan-Vincent Harre and René Heller

    Publications in astrophysics are nowadays mainly published and read in digitized formats. Astrophysical publications in both research and in popular outreach often use colorful representations of stars to indicate various stellar types, that is, different spectral types or effective temperatures. Computer generated and computer displayed imagery has become an integral part of stellar astrophysics communication. There is, however, no astrophysically motivated standard color palette for illustrative representations of stars and some stars are actually represented in misleading colors. We use pre-computed PHOENIX and TLUSTY stellar model spectra and convolve them with the three standard color matching functions for human color perception between 360nm and 830nm. The color matching functions represent the three sets of receptors in the eye that respond to red, green, and blue light. For a grid of main sequence stars with effective temperatures between 2300K and 55,000K of different metallicities we present the red-blue-green and hexadecimal color codes that can be used for digitized color representations of stars as if seen from space. We find significant deviations between the color codes of stars computed from stellar spectra and from a black body radiator of the same effective temperature. We illustrate the main sequence in the color wheel and demonstrate that there are no yellow, green, cyan, or purple stars. Red dwarf stars (spectral types M0V - M9V) actually look orange to the human eye. Old white dwarfs such as WD1856+534, host to a newly discovered transiting giant planet candidate, occur pale orange to the human eye, not white. Our freely available software can be used to generate color codes for any input spectrum such as those from planets, galaxies, quasars etc.

  2. #2
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    Jul 2005
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    Oh, excellent. Many thanks for posting that.
    George, sadly, seems not to have been around since May last year.
    We could have done with this while we were working on Celestia--I did a black-body-to-RGB conversion, but was conscious of its limitations, especially at low temperatures.

    Grant Hutchison

  3. #3
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    Quote Originally Posted by ngc3314 View Post
    Digital color codes of stars, by Jan-Vincent Harre and René Heller
    Oh, excellent! I missed this when scrolling through the Arxiv files.

    Figure 5 is missing, though.
    Do good work. —Virgil Ivan "Gus" Grissom

  4. #4
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    Jul 2005
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    Quote Originally Posted by Roger E. Moore View Post
    Oh, excellent! I missed this when scrolling through the Arxiv files.

    Figure 5 is missing, though.
    Right there at the top of page 6 in my downloaded copy, and also present in the linked document, though I needed to wait for it to fully load in my browser.

    Grant Hutchison

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