For visual observers with small optics, the colors of the deep sky range from subtle to nonexistent. Galaxies and nebulae cast too little light to stimulate the color-sensing cone cells in our retinas, so they appear pale gray-white or, in the case of a bright planetary nebulae, gray-green. Bright stars are a little more colorful. Betelgeuse appears clearly orange, even to the unaided eye, Rigel shines blue-white, and the showpiece double star Albireo in the constellation Cygnus shows off a blue-green primary and red-orange secondary in even the smallest telescope. Otherwise, star colors are quite subtle, especially to new stargazers. But there is one exception– carbon stars. These deep ruby-red stars, which dredge up nuclear soot from their innards, give off a striking glow that’s easy to see in a small telescope. See your first carbon star and you’ll want to see many more [Read more…] about The Allure of Carbon Stars
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