BM Geminorum -- Carbon Star in Gemini
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BM Geminorum at Minimum
The Carbon Star BM Geminorum was at its minimum brightness tonight. Still the red-colored
star stood out against the equally bright or brighter white stars surrounding it.

Carbon Stars are unique in that their atmospheres contain more carbon than oxygen – not so in
other stars. The carbon combines with the oxygen, forming carbon monoxide, which consumes
all the available oxygen in the star’s upper atmosphere.  The leftover carbon atoms bond with
other elements causing the star to shine ruby-red in color. No stars are darker-red than Carbon
Stars.