WZ Cassiopeiae -- Aged Carbon Star in Cassiopeia
A Ruby lost among White Diamonds
While star-hoping to the open clusters NGC 7790, 7788 and Berkeley 58 from
Caph (Beta Cassiopeiae), the carbon star WZ Cassiopeiae moved through the
eyepiece. It’s dark-red color stood out against the white background stars. I
decided as it passed through the eyepiece that I would return to this
ruby-colored star once I had finished my drawing of the three open clusters.
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.
In addition to being a carbon star, WZ Cassiopeiae is a variable due to internal
radial pulsations with two overlapping periods of 186 days and 366 days. It
varies in magnitude from 6.3 to 8.8 and shines at an average of over
17,000-times that of our sun. At the time of the drawing, I estimated that it was
shining around magnitude 7.2, putting it on the bright side of its variability. One
impressive star indeed.