Star cluster NGC 2108
3 days ago
Carbon stars are almost always cool red giants, with atmospheres containing more carbon than oxygen. Carbon monoxide forms in the outer layer of the star through a combination of these elements, until there is no more oxygen available.
Then, carbon atoms are free to form a variety of other carbon compounds, which scatter blue light within the star, allowing red light to pass through undisturbed.
A huge field of stars shines against black space. At the right, a cluster of stars is visible, packed densely together. A few larger red stars with diffraction spikes shine throughout.
Image credit: ESA/Hubble & NASA
