Benjamin Roulston

Dwarf carbon (dC) stars are main-sequence stars having more carbon than oxygen in their atmospheres. This carbon enrichment may have come from a companion star but, whatever the source, this relationship has allowed the two elements to form atmospheric carbon monoxide, cyanogen, and a variety of other carbon-based compounds.

But, in fact, the properties of dC stars are poorly understood. All are thought to be binaries most with short periods. Roulston will use the Double Spectrograph to check these assumptions against a sample of dC stars while also measuring their temperatures, rotation periods and other attributes.

A few giant carbon are readily visible in amateur telescopes. Located southeast of the star Vega, T Lyrae is a giant carbon star remarkable for its deep red color. Much larger than the objects Roulston is studying, T Lyrae is 2,345 light years from Earth and, with a mass 3 times that of the Sun, it has a diameter of 519 million miles, 600 times of our Sun. (Caltech/Palomar Observatory/STScI)