stellar classification stellar classification M dwarfs Spectral Classification M dwarfs spectral type http://astro.unl.edu/naap/hr/hr_background1.html stellar classification http://astro.unl.edu/naap/hr/hr_background1.HTML stellar classification stellar classification Spectral Classification spectra stellar classification 35,500 degrees F stellar classification stellar classification stellar classification stellar classification stellar classification stellar classification stellar classification Spectral Classification spectral types Spectral Classification of Stars http://astro.unl.edu/naap/hr/hr_background1.html early 1900’s stellar classification OBAFGKM stellar classification spectral classes spectral class