Assertion: star | /r/HasProperty | unique halfplane
Facets:
Source sentences:
text: Through any direction, or point on the celestial sphere, e.g. the position of a star, a unique [half] plane (or great [half] circle) perpendicular to the horizon can be found; this is called vertical circle; all vertical [half] circles contain (and intersect in) both the zenith and the nadir.