- Alternative form of heliocentrism.
This is the form recognized by many dictionaries as grammatically correct. However, in current usage "heliocentrism" appears to be by far more frequently used. According to a Google Books search it seems that "heliocentrism" began to gain ground in the turn of 1960s and 1970s with the first occurrence taking place in 1930s.
heliocentric + -ism < from Greek ηλιοκεντρικός (heliokentrikos) "having the sun as his centre", from ancient Greek ήλιος (helios) "sun" + κέντρον (kentron) "centre".