Jump points are found at the precise intersection of the boundary connecting with other jump points of others stars forming jump lines. This is the case when two stars are not too close together, or if they are not too light. If the antigraviton potential is right a jump ship can move along that intersection. Big stars, which "dip deeper" into the antigraviton "well" have more jump points. The boundary is not always constant and regular, as it is affected by the gravity of the planets. There's evidence pointing to the existence of "tides" in the antigraviton sea, adding to the variation.