S Cepheii – Carbon Star in Cepheus
by Glenn Chaple
This past August 15th, I presented a talk on carbon stars at the Stellafane Convention. The library at the McGregor Observatory, which served as the setting, hosts a typical audience of 12 to 20. This time, more than 30 Stellafaners showed up. The topic was obviously one of intense interest!
The reason is obvious to anyone who has ever looked at a carbon star like R Leporis (“Hind’s Crimson Star”), T Lyrae, or V Aquilae. At certain times, they can appear red – drop-of- blood red!
Popular fare for backyard astronomers over a century ago, carbon stars have enjoyed a resurgence in popularity, particularly with individuals seeking a change from the usual deep-sky fare of nebulae. clusters, and galaxies. They have become so popular that the Astronomical League recently initiated a carbon star observing program that lists 100 of these cosmic rubies.
Like its kindred carbon stars, of which nearly 7000 have been catalogued, S Cephei is a red supergiant with a ‘sooty” carbon-laced outer atmosphere that enhances its ruddy appearance. Typical of its stellar class, it varies in brightness, ranging from 7th to 11th magnitude in a period averaging 485 days.
Lest I be accused of false advertisement, I should point out that not all carbon stars are ruby red. The color you see will depend on your vision, the nature of binocular or telescope used, sky conditions, and the star’s magnitude (carbon stars tend to be reddest when near minimum brightness). At the very least, a carbon star will shine with a rich golden yellow hue.
The accompanying finder charts point the way to S Cephei. A line from gamma (γ) to the wide pair rho (ρ) and 28 Cephei and extended an equal distance beyond brings you to a triangle of 7th magnitude stars perched atop a 6th magnitude star labeled 59 (its magnitude without decimals) on Chart B. Chart C will help you star-hop from the triangle to S Cephei. Magnitudes of surrounding stars are added (decimals omitted).
You’ll find more information on S Cephei at www.aavso.org/lcotw/s-cephei. The Astronomical League’s Carbon Star Program is described at www.astroleague.org/content/carbon-star-observing-program.
Finder Charts A (www.constellation-guide.com); Finder Chart B. (AAVSO); Finder Chart C. (AAVSO)