Trojan (celestial body) whatever the planet and trojan masses. And if = , then both must exceed 13+√168 ≈ 25.9615. But all this assumes a three-body system: once other bodies are introduced, even if distant and small, stability of the system requires larger ratios. Trojan (celestial body) In astronomy, a trojan is a minor planet or moon that shares the orbit of a planet or larger moon, wherein the trojan remains in the same, stable position relative to the larger object. In particular, a trojan remains near one of the two trojan points of stability – designated and – which lie approximately 60°
Celestial sphere the equatorial coordinate system, the celestial equator divides the celestial sphere into two halves: the northern and southern celestial hemispheres. Because astronomical objects are at such remote distances, casual observation of the sky offers no information on their actual distances. All celestial objects seem equally far away, as if fixed onto the inside of a sphere with a large but unknown radius, which appears to rotate westward overhead; meanwhile, Earth underfoot seems to remain still. For purposes of spherical astronomy, which is concerned only with the directions to celestial objects, it makes no difference if this is actually the case