beyond wrote:Ann, how do you know that the red spot under 11/11 is a carbon star and not just the redshift of a star that is going away from us?
The star is SAO 98230, a magnitude 6 C6II (carbon) star (variable from 5.6 to 7.5 with a 195 day period). There are no stars which are redshifted enough to appear a different color to our eyes. That's because the only stars we can see are far too close for cosmological redshift to be a factor, and none are moving more than a few hundred kilometers per second relative to us, so Doppler redshift is also very small. Even if we could see redshifted stars, there's no assurance they would appear red, or more red than their unshifted appearance. It would all depend on their spectral characteristics. While there would be energy shifted into the red range, there might be even more blue or UV shifted into the middle or short wavelengths. So a redshifted star might appear bluer or whiter.
Are there a lot of carbon stars that would be mistaken for stars traveling away from us?
No, for the reasons given above. There are many carbon stars, but not so many as bright as this one- bright enough to appear intensely red through a telescope. BTW, the red of carbon stars is only partly related to the scattering of shorter wavelengths (as in a red sunset). These stars are very cool (<3000K), so their blackbody peak is in the red or IR, and the C2
component of their atmosphere has some strong peaks in the middle and long wave parts of the visible spectrum. So you are starting with something quite red, and then passing it through a sooty atmosphere (and likely a dusty shell, as well) further reddens the light. These stars are very striking telescopically.