Polestar

noun

2. A guiding principle.
3. The star Polaris, of the second magnitude, situated near the north pole of the heavens.
4. Hence, that which serves as a guide or director; a lodestar.
5. In biology, a polar star; one of the two stellate figures which may be borne upon the poles of the fusiform nucleus-spindle in the process of karyokinesis.