CHI CNC (Chi Cancri). Though only fifth magnitude (5.14), Chi Cancri nevertheless is part of the outline (at least that used here; others differ) of Cancer, the Crab, whose fame comes not from its bright stars but from its position in the ancient Zodiac, situated between Gemini and Leo (though its harboring of the Beehive cluster does not hurt). Don't confuse it with Chi Geminorum, which lies across the border in Gemini just 3.7 degrees to the west and is an ordinary orange K2 giant 256 light years away. Chi Cancri on the other hand is very different; as a class F (F6) hydrogen-fusing dwarf, it is not all that dissimilar from the Sun. And as a lower mass dwarf, it has to be much closer than Chi Gem, just 60 light years away (give or take under 1). From its point of view, our Sun would be a full magnitude fainter, mixed in with the stars of deep southern Capricornus. In spite of Chi Cnc's relative faintness, it's pretty popular. More than 20 temperature measures average 6270 Kelvin. With no significant correction for infrared or ultraviolet light, the star radiates at a rate 2.4 times that of the Sun, which gives it a radius of 1.30 times solar. Direct measure of angular diameter through interferometry yields a radius of 1.39 times that of the Sun, just seven percent higher, not all that bad. The mass is about 20 percent greater than that of the Sun, a more precise study giving 1.07 solar. From other studies, the age is close to that of our Sun, which because of its higher mass means that Chi Cnc is relatively older when compared with its hydrogen fusing lifetime of around 7.5 billion hears. Chi Cancri is just under the "rotation break" at class F5, hotter than which stars rotate much more rapidly as a result of a decline in their outer convective layers, which generate magnetic fields that, coupled with the stars' winds, slow them down. Chi Cnc rotates with a projected equatorial speed of just 5 kilometers per second, giving it a rotation period under 13 days. Yet the star seems to have no magnetic activity, which may have died away as a result of age. Bright dwarfs like Chi Cnc are prime targets for planet searches. Yet the star seems devoid. Especially telling, there is no evidence for any debris disk as seen around so many stars, including hotter ones like Vega. Perhaps that is related to the lower metal content, which is about half (relative to hydrogen) that of the Sun, planets rather liking higher values. The lower metal content may be related to a somewhat higher velocity through space relative to the Sun, about triple normal. Not only are there no planets (at least found), there are no companions either, the star quite alone in a lonely spot in the Zodiacal Crab.

Written byJim Kaler 4/18/14. Return to STARS.