The name says it all! Noel has just processed this Sky 90/M25C image of the bright red carbon star “La Superba” which can be found in Canes Venatici at a distance of 711 light-years:
La Superba or gamma Canum Venaticorum appears amazingly red to the observer. It is a semi-regular variable star with a visual magnitude range of 4.8 to 6.3 and a period of 158 days. It is amongst the brightest of the giant red carbon stars, this is the phase of a star’s life where energy generation is from helium-to-carbon fusion reactions. There is an abundance of carbon compounds in the star’s outer atmosphere and these molecules tend to absorb short wavelength radiation leading to the star’s very red appearance. The temperature of La Superba is very low at only 2200K which makes it one of the coolest true stars.
One of the brightest carbon stars (4400 times the luminosity of the Sun), and yet one of the coolest stars too (a rare J class carbon star at only 2200K) – try and find La Superba lying below the handle of the Plough (Ursa Major,Big Dipper). R.A. 12h 45m 07.83s Dec. -45deg 26min 24.92sec.