Apr 19, 2011

Celestial Architect Spreadsheet 1.3.1

Version 1.3 provides several usability enhancements.

  • The albedo sheet is now easier to use and harder to mess up.
  • The chart will automatically calculate your star's color and type based on mass
  • Some comments were expanded or clarified
  • Items reorganized.
The major new feature is limited support for Binary Star systems.  The calculations assume that both stars are very close to each other (technically both in the same spot), since i haven't figured an elegant way to deal with all the possibilities, and effects they might have on insolation and orbit.

Also as suggested & advised in the comments the planet is calculated from the user entering the desired surface gravity instead of mass.

EDIT:  1.3 inaccurately calculated the planet's year.  1.3.1 replaces the equation, and i've tested it with several of our solar system's planets, and gotten the right results.  So, make sure you download to 1.3.1.



  1. "The chart will automatically calculate your star's color and type based on mass"

    Stellar type is determined from spectrum. Star's color relates to temperature.

  2. The Vogt-Russell theorem tells us that we need to know the mass AND composition to uniquely determine star's radius, luminosity, and internal structure, as well as its place on the main sequence.

  3. accidentally deleted previous my previous comment:

    "Assuming a main sequence star (which my chart does) -- you can derive stellar type and temperature/color from mass. "

    Jelly: Yeah, i know metallicity has an impact. Note that my chart lists the star type/color in blue type. "Blue text indicates rough approximations"

    Also On the side there's a note:
    "Based on metal content, actual stars may vary 20%-30%"

    My purpose is to allow the less mathematically inclined to hammer out some plausible solar-system -- not to simulate every possible celestial phenomenon. So i simplify. This chart does main sequence stars of typical metallicity. It give a possible, and probable answer to star type and color. I make no claim that it's the only solution.

  4. If you want simplicity with some degree of accuracy and plausibility, the best thing here would be to assign spectral class according the luminosity and effective temperature, since you don't know the metallicity of the star in question. If you want a scientific principle in use, that is.

  5. Jelly: You haven't actually looked at the chart have you?

    "Mass" is the only variable i have for a star, thus every other detail is derived from mass.

  6. I had looked. And for my 0.8 solar mass star, which was k3v, i got G, yellow. That's why i even mentioned the whole thing.

  7. I'm not trying to be combative.

    According to my source (probably wikipedia, don't remember now), .8 sol masses is the lower limit for G (i.e. 0.79 would be K). So the 20-30% metallicity variation would make the difference between G and K.

    I've seen other numbers, but i had to go with something.

  8. I'm not trying to battle you either.

    When i entered numbers in your spreadsheet, i didn't look at the 'code' behind the stuff.
    What i'm saying, i didn't expected the simplicity. My calcualtions usually are all over the page with the whole history of my systems. I'm into the details too much. Don't mind me.

  9. I must say, I thought this was a pretty interesting read when it comes to this topic. Liked the material. . . . . architecture