* * * Analysis, sky location and images for selected entries in my Red Stars Catalog * * *
Carbon Star - X Cancri
This star is best observed during the spring months, lying not far from the famous Beehive open cluster (also known as the Praesepe or M44) in constellation Cancer. Here's an image of X Cancri I took on the evening of April 27, 2010 using my Canon DSLR, when planet Mars was passing close by:-
(X Cancri is circled, not far from the rooftop.)
X Cancri varies in apparent brightness between mag. 6.0 and 7.5, with a semiregular periodicity. This is one of the few stars whose apparent angular diameter has been approximately measured by lunar occultation. Using this method, astronomers have determined X Cancri to have a microscopic apparent disk diameter in the region of 7.9-9.0 milliarcseconds (see this article).
As with similar carbon stars in its league, the distance of X Cancri is highly uncertain given the vast error margin in its Hipparcos parallax of ~2.90 mas (±0.78), but in view of its apparent brightness and observed proper motion, the star is located 1,000 light-years away from us at the very least.
