The most current article I read was found in Sky & Telescope and titled, Colored Double Stars, Real and Imagined. In the article, the author, Bob King, leads the reader on a journey through the colors of stars and their properties. He begins the article mentioning how stars reflect light based on their temperature but get their classification based on where they fall on the H-R diagram. He pointed out the fact that what we observe may not always be what is the true essence of color the star actually gives off. King did a test of his own while employing Alan Adler’s method of determining color difference. He isolated double stars to help examine color hues the stars gave off. See picture below.
(The double star Albireo in Cygnus is a colorful favorite for any pair of binoculars or telescope. The secondary’s color varies due to complementary color contrast.
He learned that once the stars were isolated their color and spectral type were more easily viewed. As the H-R diagram shows below, the various colors emitted show the compositions and properties of the stars.
The author goes on to talk about the stars that are most widely observed which tend to be red stars and blue-white suns. Once these double stars are isolated and separated by the spectral type, the author was able to tell a little bit more about what the stars are made of and what temperature they are. King ends the article with a diagram of his own measurements.
In the lecture tutorial that we worked on in class regarding the H-R diagram (pictured below), we learned that stars of the same spectral type have the same temperature and stars of the same absolute magnitude have the same luminosity.
What I found interesting is the fact that out of all of the double stars he studied not one pair had the same spectral type. I would have loved to see the stars plotted on a blank H-R diagram. I think most of them would have fell on the main sequence if I am correct.