Carbon Star

Red giant (or occasionally red dwarf) star whose atmosphere contains more carbon than oxygen, which combine in the outer layers of the star, forming carbon monoxide and other carbon compounds. The abundance of carbon is thought to be a product of helium fusion within the star. Carbon stars are cool (2000-3000 K), deep red or brown colored, and emit most of their energy at IR wavelengths (shorted wavelengths are absorbed by atmospheric carbon). Although very large, carbon stars are difficult to detect without specialized equipment. All carbon stars are irregular or semiregular variable stars.

Many carbon stars are actually binary stars, where one star is a giant star and the other a white dwarf. The giant star loses carbon to the surface of the white dwarf, resulting in a carbon enhanced spectra. Many carbon compounds (HCN, C2N2), Li, and Zr have been detected at high levels, which have circulated from the core of the star into its upper layers.

As much as half (or more) of the total mass of a carbon star may be lost in powerful stellar winds that eject carbon-rich “dust” into the interstellar medium. This dust provides the raw materials for the creation of subsequent generations of stars. The ablated material surrounding a carbon star may blanket it to the extent that the dust absorbs all visible light.

Some or all content above used with permission from J. H. Wittke.