Observing Carbon Star Variables

Below is a list of some 27 unique stars visible in November. Each is a "Carbon Star" variable with some interesting spectral characteristics.

In the old days of stellar spectral typing, there were two categories, R and N which have been combined into one newer group called type C stars or Carbon Stars. These are giant stars with a large abundance of carbon left over from their years of nuclear fusion. Almost always these stars can be seen quite easily in a star field by their sharp red color.

The cause for this reddening is that the star's outside layers contain quantities of the carbon molecules C2 (CC), CN and CH which creates an absorbtion spectrum blocking out most blue wavelengths from the star's interior. It is also interesting to note (and you may have already noticed in the above discussion) that carbon stars are some of the few stars that are cool enough to permit molecular formation.

Observing these stars can be enjoyable. Each of these stars is a variable, usually with a long period extending well over 100 days. Their magnitude ranges can be anywhere between one and ten magnitudes which in itself can create a surprise if you're not used to seeing a star where one wasn't before! Use a wide field, low power eyepiece to start with. You can choose to star hop to the location using a star atlas, or use digital setting circles, many of which will have these stars preprogrammed into them. Once you have aligned the telescope near or on the star, the star should just pop out at you as the reddest thing in the field of view. A chart can be used to verify that you are actually looking at the carbon star of choice and not another one that's just not listed in the table below. Use higher magnifications to get the field of view most pleasing to your eye, and enjoy the view!

If you are interested in making scientific contributions, you might consider contacting the AAVSO (American Association of Variable Star Observers) located in Cambridge, MA, USA. They are the largest central data collection agency for variable star studies, and will welcome all observations from amateurs and professionals alike. Their web site can be found at: http://www.aavso.org

All data directly from:
General Catalogue of Variable Stars, 4th Edition, Volumes I-III Kholopov, P.N., Samus', N.N., Frolov, M.S., Goranskij, V.P., Gorynya, N.A., Kireeva, N.N., Kukarkina, N.P., Kurochkin, N.E., Medvedeva, G.I., Perova, N.B., and Shugarov, S. Yu.

Last Modified: 3/19/03 8:55p
This page:© Copyright 2005 by John A. Blackwell