Stars Red
Posted on Thursday, May 6th, 2010 at 8:49 pmHow can I calculate the radius of stars (incl Red giants) from Abs.Magnitude, Color Index and Spectrum?
I have seen some charts but I'm working with a relatively large database and need to be able to calculate these values quickly. The result don't have to be exact at all, but should look about right when looking at images. Are reg giants harder to work out?
Please specify radius units (Solar or km, etc) if relevant.
1. Derive a surface temperature from either the color index or spectral type.
2. Use the Stefan-Boltzmann law (http://en.wikipedia.org/wiki/Stefan-Boltzmann_law ) to calculate the luminous flux.
3. Determine the total power output from the absolute magnitude, and use that with the luminous flux to calculate the size of the star. These sites should help with the conversion factors:
http://www.astronomynotes.com/starprop/s4.htm
http://spiff.rit.edu/classes/phys301/lectures/absolute/absolute.html
http://www.go.ednet.ns.ca/~larry/astro/HR_diag.html
Once you work out the necessary constants, you should be able to make a spreadsheet or script to quickly process your data.
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